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NC Maintenance How to keep your NC in top running condition. This section focuses on maintaining and fixing the stock NC - not about modifications.



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Description: Old 21st January 2011, 05:52

  #1

Lone Wlf

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Differential Fluid Change @ 10,000 miles?


Just had my new (to me) 2010 6 speed MT in for its first oil change at 5500 miles. The mechanic suggested that at around 10k miles it might be a good idea to change the diff fluid because there could be metal shavings in it since the car's new.

I'm not mechanical enough to know whether this is a good idea or a waste of money. What do you guys think, and why?

Thanks.

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Description: Old 21st January 2011, 08:00

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Some do change early and it won't be harmful, however the mazda service schedule lists at 48 months or 60,000 miles. I did mine early at around 12,000 miles as I wanted to upgrade the brand used. I personally won't make/pay for a service visit just to do this however if it is already going to be in then I might have it done. More info from mazda below:

https://www.mymazda.com/MusaWeb/sear...2&modelId=1710

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Description: Old 21st January 2011, 09:17

  #3

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I changed the rear diff lube around 10,000 miles in my 06. I wanted to change to synthetic, and this time frame worked out well. I have the T/F limited slip diff.

The fluid was really black. "I have heard" some of the blackness came from the ring and pinion gears seating, and some from the clutch packs seating into each other. As black as it was, I am glad I changed it if for only that reason.

At 20,000 miles I put the Motorcraft XT-M5-QS in my 6 spd tranny, and thought while it was up on jack stands I might as well drain out the rear diff and refill it with the left over differential lube I had from before. The fluid that came out was only darkened a little.

My one uncle used to be in charge of a fleet of vehicles for the state, he always said that "oil and grease is cheaper than parts and labor". I tend to follow that line of thinking too.

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Description: Old 21st January 2011, 09:43

  #4

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If it's a standard diff on that 06 it probably is not critical, because it's not so precise and complicated as a limited slip version. The drain plugs on the diff and tranny have a magnet that will catch and hold filings anyway. Surprised he did not suggest the tranny ... unless he was nervous about it. Changing that fluid would be better. Search here for info on "Motorcraft Full Synthetic" for loads of info about tranny fluid for you. Even if you are not having troubles, it's nice to put some quality stuff in there for the long run.

Before you do the next oil change, post back with a price that they ask change the diff and tranny fluids. Folks will let you know if it is reasonable. It's an incredibly easy job to do yourself with a $10 hand pump to put the new fluids in. But it does involve getting the car up in the air, crawling under, etc. Depending where you are in CA, I bet you could find a member nearby to do it with you, and give you a guided tour of the bottom of your car at the same time. Well worth the effort! In fact, consider doing that for your next oil change, and installing a Fumoto valve at the same time. It will help prevent future greasemonkeys from screwing up your oil drain plug.

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Description: Old 21st January 2011, 10:22

  #5

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Quote:

Originally Posted by Lone Wlf Description: View Post

.... I'm not mechanical enough to know whether this is a good idea or a waste of money. What do you guys think, and why? ...

I changed mine at about 3k miles and glad I did. The old stuff came out black and sludgy, and there was metal present. Not saying necessarily that this is a problem, but I'm sure the baby appreciated the clean new stuff. Description: http://forum.miata.net/vb/images/smilies/biggrin.gif

Used one quart (liter?) of Mobil1 synthetic GL5 gear oil. Cost ~$10. Took about 1/2 hour to change. It came in a sorta squeeze bottle with spout, so no funnel or pump was necessary.

Changed it again at ~20k miles. Surely overkill, but babies are meant to be babied. And it's sorta satisfying to do these simple jobs yourself. Description: http://forum.miata.net/vb/images/smilies/638.gif

A much more useful alternative to the F. valve, is a "suck it out the dipstick" device. It's on my short list of must have tools. Right up there with the clamp-on DC meter and the digital vernier calipers. Description: http://forum.miata.net/vb/images/smilies/action-smiley-066.gif

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Description: Old 21st January 2011, 10:35

  #6

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Quote:

Originally Posted by Lone Wlf Description: View Post

........... What do you guys think, and why?

Thanks.

If it makes you feel better, I'd suggest you have it done, although I don't think it's necessary.

Why? I donno......just to feel better...??

Oh, have some NC Tips....Description: http://forum.miata.net/vb/images/smilies/smile.gif

http://forum.miata.net/vb/attachment...9&d=1290147156

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Description: Old 21st January 2011, 11:28

  #7

Raven18940

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I'd make sure you work the clutch packs a little before you dump the fluid if you have a LSD. Want to get all the break in wear over with to old oil so the new oil will stay clean longer.

If you have no LSD, dump it when it's convenient. 

You'll like the synthetic oil on cold mornings. I know my drivetrain feels like glue first thing in the morning when it's in the 20F's out. Why did Mazda use conventional oil in the gearbox and diff??? Description: http://forum.miata.net/vb/images/smilies/confused.gif

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Description: Old 23rd January 2011, 10:13

  #8

S2KPuddyDad

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Differential oil change on a new rear…..You should change the fluid at around 600 to 1,000 miles.
You say why??????

You are breaking in a new gear box the first few hundred miles are going to make the most friction and wear in the shortest period of time than the full life of the rear end. 
This is true of the open standard rear or the LSD equipped rear. The LSD rear has a little bit more friction going on than the standard open but both types of 3rd member share all other same components.

The NC and NB Miata rear takes just shy of a quart/liter to fill….over filling is bad….Why????? Because the oil can foam from lack of ventilation. Filling the case is easy….fill to the oil starts to come back out the fill hole. Let the oil flow back out on a level surface till it slows to a trickle/drip then replace the fill plug. The rear has a proper level doing it this way and you have no second guessing if it is right. 

What should I use for oil????? A good 75/110 or 75/140 standard or synthetic oil as long as it is a GL-5.
Stay away from Royal Purple gear lube use wall mart brand before this over priced substandard stuff.
But my book says 75/90?????? The 75/90 of old is the new 75/110 the 75/110 has taken the place of the 75/90 in lubricating properties.

What brand of oil should I use? Amsoil brand is the best and the best priced for the top of the line lubricants. Mobil 1, Red Line, Valvoline are also very good choices.

Change the fluid again in 5000 miles doing this will get the rest of the break in debris out. Refill and change ones a year or 2. The total cost of this doing it your self is about $45 on the high side and $30 on the low side. It’s cheap insurance to assure a proper long lasting gear box. 

Be sure to inspect and clean the magnetic drain plug. If you see large metal pieces or heavy metallic in the oil this is cause for inspection under warranty. There is always going to be some metallic on the drain plug and in the old oil this is normal. 

Do a little research on all I tell you, you will understand I’m not giving opinion just fact.

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Description: Old 23rd January 2011, 17:49

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^........very good, informative post, S2KPuddyDad .......Description: http://forum.miata.net/vb/images/smilies/smile.gif

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Description: Old 23rd January 2011, 19:21

  #10

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Point of info for new readers on the forum: S2KPuddyDad is a specialist in rear ends, and we're talking about the metal kind in his avatar, not the other kind. So his post here is the authoritative final word. Ignore everything hacks like me said before.

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Description: Old 23rd January 2011, 20:35

  #11

Raven18940

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I don't understand the logic of using 75W-140 instead of 75W-90. Everyone seems to be moving to lighter oils that reduce drag (5W-20 instead of 5W-30 for example). Why the reversal of the trend?

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Description: Old 23rd January 2011, 21:40

  #12

S2KPuddyDad

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Originally Posted by Raven18940 Description: View Post

I don't understand the logic of using 75W-140 instead of 75W-90. Everyone seems to be moving to lighter oils that reduce drag (5W-20 instead of 5W-30 for example). Why the reversal of the trend?

There is nothing trendy about gear box lubricant. The design of the hypoid differential gear box is old school and has not been improved on like the engine and transmissions have been over the years.

The Mazda gear box differential calls for a SAE 90W from the factory using a 75/90w may not give adequate protection. Your safe bet is a 75/110 GL-5 hypoid oil. 

In 2006 the oil standards changed Please read, 


“The need for redefined classifications centered on the wide variation in kinematic viscosity possible for SAE 90 and SAE 140 grade lubricant. In the prior version of SAE J306, these ranges were so broad that lubricant viscosity could vary greatly and still technically be in grade. Two new viscosity grades were introduced to cover the upper end of the specifications, SAE 110 and SAE 190. The more narrowly defined classification provides OEMs with greater flexibility in specifying a viscosity grade to ensure an optimal balance of fuel economy and durability for their equipment.

In addition, under the old designations, an axle could be serviced with a lubricant having a viscosity significantly lower or higher than the lubricant with which the axle was validated. To prevent the axle from being filled with a lubricant with too low a viscosity, an OEM was forced to specify a higher viscosity grade than actually desired.

For example, under the old classifications, if the optimum 100°C viscosity for an axle was 19.5 cSt, the OEM would normally specify an SAE 90 lubricant. However, the actual viscosity of this lubricant could be as low as 13.5 cSt, which might be too low to provide the required durability. To prevent this problem, the OEM would recommend an SAE 140 grade lubricant, ensuring that viscosity would never fall below 19.5 cSt. Unfortunately, that also means viscosity could be as high as 41.0 cSt, possibly resulting in poor fuel economy or shift problems. Under the new limits, the OEM would recommend SAE 110 grade lubricant, which meets the 19.5 cSt requirements and ensures that the axle is serviced with a lubricant having a viscosity no higher than 31 cSt.

A Question of Balance 

OEMs are challenged today to meet the often conflicting demands for improved fuel economy coupled with improved axle durability. Government regulations are dictating better fuel economy, while vehicle owners are demanding increased performance. Engine horsepower has increased by 34% over the last decade, but axle gear sizes have remained constant, sump capacities have been reduced, and drain intervals have been extended. These demanding conditions can be met only by axle lubricants that provide enhanced durability protection.

Axle efficiency can be improved by using lower viscosity fluids (such as SAE 75W-90), which minimize frictional churning losses. However, light trucks and SUVs are often used in conditions that expose axles to heavy loads or high operating temperatures. These conditions require superior axle protection, often provided by choosing a heavier viscosity fluid (SAE 75W-140, for example). Commercial vehicle applications may have even more stringent durability requirements. However, providing high durability and long vehicle life often reduces fuel efficiency.

The new viscosity classifications provide more flexibility for OEMs to select the optimum viscosity grade for an application. For example, the SAE 110 grade should be useful in an SUV or light duty truck where improved fuel economy is important but high torque or durability at high speed operation is essential. This new classification should aid OEMs in specifying a fluid viscosity more tightly to ensure that the lubricant has the intended physical properties for a given application.

The SAE 190 grade may allow better efficiency and enable multigrade performance in severe duty applications where high film strengths are needed. These end uses may include applications such as construction equipment operated in extreme temperature environments. The end result is a better match of fluid performance to axle needs.

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Description: Old 23rd January 2011, 22:26

  #13

Raven18940

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Originally Posted by S2KPuddyDad Description: View Post

The Mazda gear box differential calls for a SAE 90W from the factory using a 75/90w may not give adequate protection.

I fail to see how a 75W-90 oil doesn't meet the viscosity requirements of a SAE 90 oil. The 90 is the important number in 75W-90, it means it conforms to SAE 90 specs at operating temperature. The 75W only means it's thinner than SAE 90 when cold, like yesterday when it's 18F outside here. That SAE 90 gear oil felt like glue. Description: http://forum.miata.net/vb/images/smilies/rolleyes.gif

Anyway, back on topic. Since it says the manufacturers are specing thicker oils than they need so their diffs always have oil thick enough, it seems reasonable to assume that any SAE 90 should fit the bill. However, the real question here is what is the the viscosity of the OEM oil because then it should be fairly easy to find a multi-grade synthetic to match.

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Description: Old 23rd January 2011, 22:37

  #14

S2KPuddyDad

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Originally Posted by Raven18940 Description: View Post

I fail to see how a 75W-90 oil doesn't meet the viscosity requirements of a SAE 90 oil. The 90 is the important number in 75W-90, it means it conforms to SAE 90 specs at operating temperature. The 75W only means it's thinner than SAE 90 when cold, like yesterday when it's 18F outside here. That SAE 90 gear oil felt like glue. Description: http://forum.miata.net/vb/images/smilies/rolleyes.gif

Anyway, back on topic. Since it says the manufacturers are specing thicker oils than they need so their diffs always have oil thick enough, it seems reasonable to assume that any SAE 90 should fit the bill. However, the real question here is what is the the viscosity of the OEM oil because then it should be fairly easy to find a multi-grade synthetic to match.

It is a long read but the answer is there. Some brands of 75/90 will fall below safe standards for our rear requirements. If you wish to use 75/90 go to your brand of choice web site and find out if it meets the standards many do not.

Or even more easy…..USE 75/110 it’s a no brainerDescription: http://forum.miata.net/vb/images/smilies/wink.gif

Just a little FYI to you track junkies use 75/140 or an SAE 190 the stock LSD will perform much betterDescription: http://forum.miata.net/vb/images/smilies/638.gif

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Description: Old 23rd January 2011, 22:51

  #15

Raven18940

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Originally Posted by S2KPuddyDad Description: View Post

It is a long read but the answer is there. Some brands of 75/90 will fall below safe standards for our rear requirements. If you wish to use 75/90 go to your brand of choice web site and find out if it meets the standards many do not.

My question is what are the "safe" standards? What cSt at 100C? Description: http://forum.miata.net/vb/images/smilies/confused.gif Will the 15.2 cSt of M1 75W-90 meet the specs or does the oil need to be thicker?

EDIT: Basically, I may not know everything about rears, but I know a lot about oil. I'm open to using non-factory spec oil, but not without damn good reason. The gear oil standard change has been in effect as long as the NC has been around, so I don't really buy the "110 is the new 90" argument.

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Description: Old 23rd January 2011, 23:15

  #16

S2KPuddyDad

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Originally Posted by Raven18940 Description: View Post

My question is what are the "safe" standards? What cSt at 100C? Description: http://forum.miata.net/vb/images/smilies/confused.gif Will the 15.2 cSt of M1 75W-90 meet the specs or does the oil need to be thicker?

EDIT: Basically, I may not know everything about rears, but I know a lot about oil. I'm open to using non-factory spec oil, but not without damn good reason. The gear oil standard change has been in effect as long as the NC has been around, so I don't really buy the "110 is the new 90" argument.

Since our rear requires a SAE 90W you need a cst of 19.5
This is why the change and why the old 75/90 is the new 75/110
You need to use 75/110

Also note your owners manual states no 75/90 available through Mazda for your differential 
SAE 90W or 80/90W as a second
2 main reasons for diff failure is driver error and inadequate lubrication

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Description: Old 24th January 2011, 08:22

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Raven18940

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Originally Posted by S2KPuddyDad Description: View Post

Since our rear requires a SAE 90W you need a cst of 19.5

See, this is the disconnect here. Because if I read the specs right SAE 90 should be a minimum of 13.5, not 19.5. So how do you know they meant 110 when they said 90? Maybe they meant 90? The MX-5 isn't exactly a torque monster.

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Description: Old 24th January 2011, 09:25

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S2KPuddyDad

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Originally Posted by Raven18940 Description: View Post

See, this is the disconnect here. Because if I read the specs right SAE 90 should be a minimum of 13.5, not 19.5. So how do you know they meant 110 when they said 90? Maybe they meant 90? The MX-5 isn't exactly a torque monster.


Most 75/ 90w will fall below 13.5 this number is not a safe minimum. Standards are 19.5 for your Miata differential.
The Miata diff case only holds about 900ML of fluid not much for a lot of heat and shear going on inside our differential.
If you need more reassurance please do more research on your computer or just use what you think is best....Good luckDescription: http://forum.miata.net/vb/images/smilies/smile.gif

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Description: Old 24th January 2011, 09:31

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Quote:

Originally Posted by Raven18940 Description: View Post

See, this is the disconnect here. Because if I read the specs right SAE 90 should be a minimum of 13.5, not 19.5. So how do you know they meant 110 when they said 90? Maybe they meant 90? The MX-5 isn't exactly a torque monster.

If you were to ask over in the lubrication section you might get more answers. Whether or not they'll agree with what's been recently said, I have no idea, but it will make an interesting read.

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Description: Old 24th January 2011, 09:33

  #20

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Originally Posted by RubyDoo Description: View Post

S2KPuddyDad is a specialist in rear ends, ... So his post here is the authoritative final word.

Except I'd use something in the 75W-90 range, a GL-5, run it to 30,000 miles before changing it, and there is nothing special about Amsoil. Other than that, he's spot on. Description: http://forum.miata.net/vb/images/smilies/biggrin.gif

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Description: Old 24th January 2011, 10:53

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S2KPuddyDad

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Since 2006 75/90W in general (check your brand of use for there tech info) is no longer meeting the minimum safe operating standards for the differential. This is not my doing or is it because I say so.....IT IS FACT BY YOUR MANUFACTURER AND BY THE OIL INDUSTRY AT LARGE.
You can continue to use 75/90W and find no notable effect or issue but you take that chance. 

Be an informed consumer check the brand of oil that you use web site. Check the numbers (all of them that concern your use) then at that point you will know if the brand and type/blend of oil in question is the right oil for your needs. 


Please adjust your thinking.......This is what the oil people want you to do!
75/110W is now the Minimum safe oil to use if your gear box required 75/90W

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Description: Old 24th January 2011, 11:05

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Originally Posted by S2KPuddyDad Description: View Post

Most 75/ 90w will fall below 13.5 this number is not a safe minimum. Standards are 19.5 for your Miata differential.
The Miata diff case only holds about 900ML of fluid not much for a lot of heat and shear going on inside our differential.
If you need more reassurance please do more research on your computer or just use what you think is best....Good luck
Description: http://forum.miata.net/vb/images/smilies/smile.gif

See, I use synthetic oil so I'm not worried about the oil not being the viscosity that it's supposed to be. Mobil 1 is pretty on the ball with such things. 

Now you say that 19.5 cSt is the spec, which is fine by me, but how do you know this? Where did 19.5 come from?

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Description: Old 24th January 2011, 11:52

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Originally Posted by Raven18940 Description: View Post

See, I use synthetic oil so I'm not worried about the oil not being the viscosity that it's supposed to be. Mobil 1 is pretty on the ball with such things. 

Now you say that 19.5 cSt is the spec, which is fine by me, but how do you know this? Where did 19.5 come from?

synthetic or standard oil makes no difference the numbers are the numbers.
Please check the manufactures specs and minimums of the blend you use.

The number is the standard for this type of gear box.

I can't keep posting it is getting redundant. At this point please others chime in with fact not opinion. All that are in question about the brand oli and blend they use check your manufactures spects and minimums or if you have no time for this debate just use 75/110W again it's a no brainer

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Description: Old 24th January 2011, 11:56

  #24

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Quote:

Originally Posted by S2KPuddyDad Description: View Post

... The number is the standard for this type of gear box....

Where can we find that? Supporting documents??

Quote:

I can't keep posting it is getting redundant

You keep asserting the 19.5 number, but don't tell us where to check that. Description: http://forum.miata.net/vb/images/smilies/confused-smiley-013.gif

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Description: Old 24th January 2011, 13:54

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Quote:

Originally Posted by wooo Description: View Post

Where can we find that? Supporting documents??

You keep asserting the 19.5 number, but don't tell us where to check that. 
Description: http://forum.miata.net/vb/images/smilies/confused-smiley-013.gif

I don't mean to be short or be none informative about a question. I called Honda a few years back and asked. You can call Mazda and do the same. The Mazda, Honda, KIA along with others use the Mazda 3rd member design. 

The oil manufacturing industry it putting the information out to all auto manufactures the changes in oil ratings.
Everything is changing Toyota now uses a straight weight engine oil in all new autos and trucks being made now.

The hypoide gear box has not changed but oil has we all must keep up.

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Description: Old 24th January 2011, 14:35

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When I get time I will call Richmond and a few others to ask what there minimum and maximums are. I know Richmond gear company recommends 75/140 for all their hypoid gears they make.

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Description: Old 24th January 2011, 15:46

  #27

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Does Richmond make the stock rear?

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Description: Old 24th January 2011, 17:32

  #28

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Originally Posted by Raven18940 Description: View Post

Does Richmond make the stock rear?

No, but they do make 7" hypoid gears that fit our 3 rd member.

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Description: Old 24th January 2011, 18:18

  #29

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Quote:

Originally Posted by S2KPuddyDad Description: View Post

I don't mean to be short or be none informative about a question. ....

So basically you don't know what Mazda recommends for the NC's diff. That 19.5 business was just made up.

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Description: Old 24th January 2011, 18:48

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Quote:

Originally Posted by wooo Description: View Post

So basically you don't know what Mazda recommends for the NC's diff. That 19.5 business was just made up.


Wow....the Mazda rear is the same as the Honda the number is Honda and will translate to Mazda as it is the same.

This is just not our rear it is the type of gear box in general.


I don't get it, it is explained in the TSB I posted. I don't make this crap up I'm not educated at this level. You take the information your given and you pass it along. Don't shoot the messenger.....
The TSB states that MOST 75/90 oils will fall below Industry standards for minimum protection. For me and my 25k investment I will take the information and use the 75/110 as the oil companies tell me.

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Description: Old 24th January 2011, 18:54

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Originally Posted by S2KPuddyDad Description: View Post

...I don't get it, it is explained in the TSB I posted. ....

TSB?

Which of your posts contains this TSB?

Whose TSB is it?

Is it a Mazda TSB?

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Description: Old 24th January 2011, 19:04

  #32

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It appears that the OMs and WSMs for NCs of all years recommend 75W-90 or 80W-90 for the diff.

Is Mazda wrong in this, or out of date? Surely if Mazda thought 75W-110 was required they would have said so.

Is Mobil wrong in saying that their Synthetic 75W-90 is suitable for differentials?

This is puzzling.

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Description: Old 24th January 2011, 19:20

  #33

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Unable to locate the 110 stuff I decided to go with Castro Synthetic GL5. Impressed by the spec sheet approvals. Its a 15 that I will live with.

http://www.castrol.com/liveassets/bp...CANTS_3750.pdf

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Description: Old 24th January 2011, 19:28

  #34

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Quote:

Originally Posted by wooo Description: View Post

It appears that the OMs and WSMs for NCs of all years recommend 75W-90 or 80W-90 for the diff.

Is Mazda wrong in this, or out of date? Surely if Mazda thought 75W-110 was required they would have said so.

Is Mobil wrong in saying that their Synthetic 75W-90 is suitable for differentials?

This is puzzling.

I call it a TSB because it reads as such....

Our owners book says SAE 90w or 80/90w (75/90* not available from Mazda)

The oil companies changed ratings to better narrow the range of use and to bring it all under a global standard as I understand it.
The 75/110 is more in line and in the range of standard use now. 
75/140 for trucks SUV and towing and SAE190 SAE250 for sever use.

Take note to your auto parts stores gear oil selections….Before it was 90w or 75/90 now you have up to a half dozed blends to chose from.

Here is more about it,
http://www.lubrizol.com/DrivelineAdd...arOil/GL5.html

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Description: Old 24th January 2011, 20:01

  #35

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Actually I just sawy 75W90, 80w90, and a few 75W140.

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Description: Old 24th January 2011, 20:42

  #36

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I'm sorry you did not find more. Here is more info on oil via the manufactures 

http://www.mobil.com/USA-English/Lub...LS_75W-90.aspx

Amsoil touches on the subject here

http://synthetic-motor-oil-air-filte...0-gear-oil.htm

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Description: Old 24th January 2011, 20:51

  #37

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Quote:

Originally Posted by wooo Description: View Post

So basically you don't know what Mazda recommends for the NC's diff. That 19.5 business was just made up.

Quote:

Originally Posted by wooo Description: View Post

It appears that the OMs and WSMs for NCs of all years recommend 75W-90 or 80W-90 for the diff. Is Mazda wrong in this, or out of date? Surely if Mazda thought 75W-110 was required they would have said so.

Remember that this is the same Mazda that recommended GL4 OR GL5 for the tranny (do they still?), even though many of us have discovered that GL5 is problematic for the syncros and the GL4 Motorcraft cleans up a GL5 problem in time.

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Description: Old 24th January 2011, 21:27

  #38

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Originally Posted by RubyDoo Description: View Post

Remember that this is the same Mazda that recommended GL4 OR GL5 for the tranny (do they still?), even though many of us have discovered that GL5 is problematic for the syncros and the GL4 Motorcraft cleans up a GL5 problem in time.

At this point I don't have an opinion on the matter. I am just trying to gather facts on which to base an opinion.

I'm not getting an answer on why Mazda is still recommending 75W-90, well after the GL5 spec was revised and new categories created.

S2K seems to be saying that an oil with 15 cSt is too thin to be used in diffs, yet he then points us to the Mobil 75W-90 spec sheet. 

Quote:

•Mobil 1 Synthetic Gear Lubricant LS 75W-90 is SUITABLE for use in modern high performance automobiles like SUV's, Vans and Light duty trucks requiring API GL-5 level performance
•Mobil 1 Synthetic gear Lubricant LS 75W-90 is intended for initial fill, topping-off or refilling differentials,

He may very well be correct in suggesting a heavier oil for the diff but he's doing a poor job of convincing me of that. Not getting answers to asked questions isn't helping.

As I said previously, puzzling.

Too bad this isn't in the lube section where the tribologists hang out, and could chime in on this matter.

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Description: Old 24th January 2011, 22:28

  #39

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I posted Mobil 1 specs for you to see not to recommend. I also posted Amsoil to compare with some explanation of the range of theses blends. 

I have not evaded your question(s) I think I answered them to the best of my ability and recollection. I never talked or Emailed the engineers at Mazda I did talk to customer service at Honda motor Co USA some years ago and was given a range of 19 to 32 cst as a safe range for general use of the S2000 Differential. I was told to use SAE90W as per my S2000 owners manual. Maybe the person I talked to was wrong I don’t know???

Honda dealers never sold and Honda motor Co never made a differential oil for the S2000. There are countless horror stories of the dealers using Honda CRV transaxle fluid in S2000 rears. The owner did not get down the road far before the rear would fail. 
My S2000 manual does not give any other oil choice but GL-5 SAE90W


The oil companies are putting this out there for us to know that you have better choices. They are telling us that 75/110 will protect our investment better with out compromise.

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Description: Old 24th January 2011, 23:15

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Quote:

Originally Posted by wooo Description: View Post

At this point I don't have an opinion on the matter. I am just trying to gather facts on which to base an opinion.

I'm not getting an answer on why Mazda is still recommending 75W-90, well after the GL5 spec was revised and new categories created.

He may very well be correct in suggesting a heavier oil for the diff but he's doing a poor job of convincing me of that.

+1 

I was thoroughly confused by this thread, and a bit concerned, because I just replaced all the differential and transmission oils in my two Subarus with 75w90 because that's what's specified. 
(Don't even ask why a guy called Bimmer on a Miata site has two Subarus.) 


So, I went to BITOG and found this:

Before 2001 or so these are the grade ranges of 90 and 140
90: 13.5cSt to <24cSt at 100C (212F)
140: 24cSt to <41cSt at 100C

Now:
90: 13.5cSt to <18.5cSt at 100C
110: 18.5cSt to <24cSt at 100C
140: 24cSt to <32.5cSt at 100C
190: 32.5cSt to <41cSt at 100C


FWIW, this is from a thread on BITOG titled "Ford switch 80w-90 to 75w-140 synthetic." Of course, Ford made that switch in 2001 or so...

Also, see this: 
http://www.lubrizol.com/DrivelineAdd...fications.html

I still have no idea where Puddy's 19.5cSt number came from, but the MAXIMUM viscosity for 90-weight oil seems to be 18.5cSt @ 100c, so if Honda really spec'ed a 19.5cSt, then that would indeed be a 110-weight oil. 

Otherwise, if since '01 (or better, since the NC appeared in '05) Mazda says 75w90, then they presumably mean 75w90, not 75w110 or anything else. 

And I just checked, and the Redline 75w90NS I put in my transmission has a viscosity of 15.6cSt, and the Redline 75w90 for the differentials is 16.4. I'll sleep well tonight!

YMMV,

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Description: Old 24th January 2011, 23:44

  #41

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Quote:

Originally Posted by Bimmer Description: View Post

Also, see this: 
http://www.lubrizol.com/DrivelineAdd...fications.html

I still have no idea where Puddy's 19.5cSt number came from... the maximum viscosity for 90-weight oil seems to be 18.5cSt @ 100c.


Bimmer


customer service at Honda motor Co USA some years ago and was given a range of 19 to 32 cst as a safe range for general use of the S2000 Differential. I was told to use SAE90W as per my S2000 owners manual. Maybe the person I talked to was wrong I don’t know???

I also stated that some not all brands fall below standards. I said it would be best to check your brand of choice specs. Red Line has a high number it is one of the better brands to use as is Amsoil.

I am not an oil guy I just read that the 75/110 is a better choice and covers a better range.

I told my self never get into a oil thread on line you will always find strong opinion that can escalate into hard debate or hard feelings.
I don’t want anyone to be angry with me over what I was told via a phone call 4+ years ago, I am thinking this information was wrong. 
I do not know everything about oil. I only know what I was told and what I read and use this information as what I think best for me. Seeing the numbers I still feel that the 75/110 is the better choice.

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Description: Old 25th January 2011, 00:15

  #42

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Quote:

Originally Posted by S2KPuddyDad Description: View Post

customer service at Honda motor Co USA some years ago and was given a range of 19 to 32 cst as a safe range for general use of the S2000 Differential.

This sounds like the old 140 weight spec...

Quote:

Originally Posted by S2KPuddyDad Description: View Post

I also stated that some not all brands fall below standards. I said it would be best to check your brand of choice specs.

I doubt that any name brand oil does NOT meet standards. Even if they did, I doubt that they would pubicize specs that didn't meet standards. 

Quote:

Originally Posted by S2KPuddyDad Description: View Post

I am not an oil guy I just read that the 75/110 is a better choice and covers a better range... 
Seeing the numbers I still feel that the 75/110 is the better choice.

I'm not trying to bust your chops. I've seen your other posts, and the only reason I would NOT send a differential to you would be if I could find somebody out here on the Left Coast who could do it...

I'm just trying to make sure I'm using the right gear oil. 

FWIW, I doubt that using 110 weight instead of 90 weight oil would make much difference (maybe a slight loss of power and efficiency).

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Description: Old 25th January 2011, 00:38

  #43

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I have done a lot of reading as a result of this thread and have come to the conclusion that 75-110 is a better choice than 75w-90 and should be my first choice for my next differential change but this time I am going with Castrol 75w90.

I should mention that my differential was recently replaced for a whine at 50 and 70mph.

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Description: Old 25th January 2011, 06:49

  #44

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Quote:

Originally Posted by S2KPuddyDad Description: View Post

I told my self never get into a oil thread on line you will always find strong opinion that can escalate into hard debate or hard feelings.
I don’t want anyone to be angry with me over what I was told via a phone call 4+ years ago, I am thinking this information was wrong. 
I do not know everything about oil. I only know what I was told and what I read and use this information as what I think best for me. Seeing the numbers I still feel that the 75/110 is the better choice.

No one is attacking you or angry with you. You were just a bit adamant that 19.5 was the correct number and we had no idea where it had come from. 

But since that number came from a phone call to Honda, I'll just try emailing Mazda with a very specific question and hopefully it'll get bumped to a lubrication engineer who understands what I'm asking. If that doesn't work I'll just drain the oil and have the viscosity tested. Description: http://forum.miata.net/vb/images/smilies/tongue.gif

As an aside to those that want to use 75W-110, but would prefer Mobil 1, mix 75W-90 and 75W-140 in equal parts and you should have a nice 75W-110. Description: http://forum.miata.net/vb/images/smilies/638.gif

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Description: Old 25th January 2011, 07:46

  #45

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Quote:

Originally Posted by S2KPuddyDad Description: View Post

... I have not evaded your question(s) I think I answered them to the best of my ability and recollection. ...

I don't see any answer to this:

Quote:

Whose TSB is it?

Is it a Mazda TSB?

Way back you said:

Quote:

Since our rear requires a SAE 90W you need a cst of 19.5

How can that be true since we now know that the standard for 90 weight ( since 2001?) is 13.5 to 18.5 cSt?

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Description: Old 25th January 2011, 07:51

  #46

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Originally Posted by S2KPuddyDad Description: View Post

... I also stated that some not all brands fall below standards. ....

Please give an example of just one diff oil that falls below "standards"?

And you might explain what you mean by standards in this context.

I suspect you are saying that 75W-90 oils don't meet the 19.5 cSt number that you have declared a standard. But daaahhh the SAE spec "standard" for 75W-90 tops out at 18.5 cSt.

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Description: Old 25th January 2011, 07:58

  #47

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Quote:

Originally Posted by S2KPuddyDad Description: View Post

... The oil companies are putting this out there for us to know that you have better choices. ....

What oil companies are putting "this" out there? You haven't told us that, you didn't say who authored that so called TSB. I suspect the answer is Amsoil.

What manufacturers are actually making/selling 75W-90? All I have found so far is Amsoil and a couple of other boutiques. What about any of the large manufacturers.

You seem to have a tendency to exaggerate, as in a few becomes all, a phone call becomes a standard. This doesn't help your credibility. Description: http://forum.miata.net/vb/images/smilies/frown.gif

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Description: Old 25th January 2011, 08:23

  #48

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I have admitted I may have/was misinformed I also admit I do not know enough about oil to hang with you in this thread. 
I will continue to use 75/110 as it has a wider range of protection.

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Description: Old 25th January 2011, 08:29

  #49

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Just read the manual for myself. It specifies the following grades as acceptable for the rear: API GL-5 of viscosity SAE 90, 80W-90, or 75W-90. Unless Mazda gets back to me with a specific number, these are the specs I will follow.

Quote:

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I will continue to use 75/110 as it has a wider range of protection.

Thicker does not necessarily mean more protection.

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Description: Old 25th January 2011, 08:43

  #50

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Originally Posted by Bimmer Description: View Post

And I just checked, and the Redline 75w90NS I put in my transmission has a viscosity of 15.6cSt, and the Redline 75w90 for the differentials is 16.4. I'll sleep well tonight!
Bimmer

Bimmer,.. Thanks for the numbers on the Redline 75w-90. I have that in my diff now, so I feel better about that reading the above.

But I wanted to comment on the 75w-90NS you have in the tranny. I first tried that in my previous 02 Miata 5spd and was not happy with it. It was a little better than the "dino" lube, but still not good. I called and spoke with Dave at Redline, and he explained "why".

Dave told me the 75w-90NS is a compromise lube. It has some anti slip agents in it to help the snychros grip, but it also has some slip agents in it to help ring and pinion gears to slip. This is a compromise lube for TRANSAXLES. He did not recommend it for a separate manual transmission.

I then drained it out of my tranny and installed the Redline "MT-90", 75w-90 fluid. After the lube washed the slip agents off of the snychros, it made a big difference in the smoothness of the shifting. I loved it!

So if you are using the 75w-90NS in a transaxle, then you are OK. But I was a lot happier with the MT-90 in that 5 spd Manual Transmission.

Just a FWIW,.... Description: http://forum.miata.net/vb/images/smilies/smile.gif

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Description: Old 25th January 2011, 08:59

  #51

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If you Google 75W-110 most of the responses are from forums discussing the topic, and Amsoil blurbs.

Here is a link to Amsoil:

http://www.amsoil.com/storefront/svt.aspx

Quote:

... AMSOIL SEVERE GEAR® (75W-110) provides superior performance and replaces competitors’ 75W-110, 75W- 90 and 80W-90 gear oils. It delivers better viscosity protection than SEVERE GEAR 75W-90 and better fuel efficiency than SEVERE GEAR 75W-140. ...

So what do we know, or think we know, the known knowns?

- The 75W-90 spec was split in two, and the 110 took the high end.

- Mazda continues to recommend the new 90 for the NC.

- I can't find much in the way of car makers recommending the 110.

- I can't find any top tier lubricant makers selling a 110.

- Amsoil is all for the 110.

- I don't see any big downside to using the 110, but is there any advantage?

- We each will have to make our own decision until a trusted tribologist tells us what to do.

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Description: Old 25th January 2011, 09:30

  #52

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I think I understand where the cSt=19.5 may have come from. The range for 90W is 14-25. If you average that you get 19.5. 

Is that just lucky math?

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Description: Old 25th January 2011, 09:34

  #53

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Quote:

Originally Posted by aemericas Description: View Post

... The range for 90W is 14-25. ...

Isn't that is a was?

19.5 is conveniently close, but not too, to Amsoil's 20.3 for it's 75W-110. Description: http://forum.miata.net/vb/images/smilies/confused-smiley-013.gif

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Description: Old 25th January 2011, 11:32

  #54

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So I just heard back from Mazda...they referred me to page 8-18 of the manual. Yup, they referred me to the page on engine oil for my differential oil question. Description: http://forum.miata.net/vb/images/smilies/confused-smiley-013.gif

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Description: Old 25th January 2011, 12:21

  #55

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Quote:

Originally Posted by wooo Description: View Post

Isn't that is a was?
19.5 is conveniently close, but not too, to Amsoil's 20.3 for it's 75W-110

Yes, I should have said "was". The information available is confusing, but what I've been able to find is that the old 90W had a range of 13.5-24 (average 19.5). In 2006 sae j306 changed to narrow the range of 90W to 13.5-18.5 and added 110W 18.5-24 cSt

http://www.lubrizol.com/J306.aspx?id=33216&terms=J306

An interesting quote (which has the 19.5 value) from that page

Quote:

For example, under the old classifications, if the optimum 100°C viscosity for an axle was 19.5 cSt, the OEM would normally specify an SAE 90 lubricant.

Sooooo, Amsoil's 75W-110 falls in the range of the "old" 90W and would appear to be a good selection assuming that Mazda's recommendations were based on the old 90W standard. 

Given that I have an 06 which was actually built in 05 and probably designed before that, what are the chances that my Owner's manual was referring to the old SAE J306 standard or the revised 2006 version?

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Description: Old 25th January 2011, 12:36

  #56

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Quote:

Originally Posted by aemericas Description: View Post

Given that I have an 06 which was actually built in 05 and probably designed before that, what are the chances that my Owner's manual was referring to the old SAE J306 standard or the revised 2006 version?

Well you could go by my 2010 manual which still specs SAE 90 oil.

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Description: Old 25th January 2011, 13:03

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Originally Posted by Raven18940 Description: View Post

Well you could go by my 2010 manual which still specs SAE 90 oil.

Even the Amsoil website lists 80W-90 and 75W-90 as recommended. It does list 75W-110 too.

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Description: Old 25th January 2011, 13:05

  #58

cheetahdriver

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well, sort of, but not so much....


Quote:

Originally Posted by S2KPuddyDad Description: View Post

Since our rear requires a SAE 90W you need a cst of 19.5
This is why the change and why the old 75/90 is the new 75/110
You need to use 75/110

Also note your owners manual states no 75/90 available through Mazda for your differential 
SAE 90W or 80/90W as a second
2 main reasons for diff failure is driver error and inadequate lubrication

while the 19.5cSt number you are getting is right in the middle of the pre-revision 90wt range, it does not necessarily mean that you need a 19.5cSt lubricant to adequately lubricate a miata diff. 

the old range for 90wt was 13.5-23.9. since the miata diff specs were done during this period, it is safe to assume that a 13.6cSt lubricant will do the job. most of the XXw90 and straight 90wt lubricants are all formulated toward the light end of the scale (one of the very reasons that the revision took place). since the current miata still specs a 90wt, i am fairly certain that you don't need a 19.5, or a 22cSt oil to adequately lubricate the rear end. as most people have been using a 13.5-15cSt lubricant all along, and there have been no rash of diff failures, i would be happy to call that empirical proof and move on. 

a heavier lubricant in the rear end will just make it run hotter, and use more fuel. 

for those interested in the mechanics of it, a very good table that i have posted before is

http://www.lubrizol.com/DrivelineAdd...fications.html

<edit> well, there was a whole 'nuther page showed up while i was posting this (and taking calls). i see most got there while i was typing<G>

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Description: Old 25th January 2011, 13:07

  #59

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Since changing the differential oil was on my to do list for today and I've been reading this thread, I stopped at the dealer before picking up lubricant. The service manager (who I have a fair amount of respect for), looked at a couple of factory books, looked online (at what I don't know) and said that the recommendation is as printed in the owners manual of my 08. He then pointed to a 55 gallon drum of Castrol 80/90 which is what they use for a rear differential change, and then pointed to a 55 gallon drum of something else from Mazda which is for front wheel drive systems only. That was good enough for me, bought a quart of Castrol 80/90 from the dealership and will put that in there and drive with peace of mind. Now, I have an automatic so no LSD so others may benefit more form something else.

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Description: Old 25th January 2011, 15:07

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Quote:

Originally Posted by cheetahdriver Description: View Post

the old range for 90wt was 13.5-23.9. since the miata diff specs were done during this period, it is safe to assume that a 13.6cSt lubricant will do the job. most of the XXw90 and straight 90wt lubricants are all formulated toward the light end of the scale (one of the very reasons that the revision took place). since the current miata still specs a 90wt, i am fairly certain that you don't need a 19.5, or a 22cSt oil to adequately lubricate the rear end. as most people have been using a 13.5-15cSt lubricant all along, and there have been no rash of diff failures, i would be happy to call that empirical proof and move on.

Welcome to the flaw in the argument I pointed out two pages ago. Description: http://forum.miata.net/vb/images/smilies/wink.gif

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Description: Old 25th January 2011, 15:14

  #61

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If the notion of trading a little gas mileage for more diff protection bothers you, by all means buy the 90. If the notion of trading a little diff protection for some gas mileage bothers you, buy the 110 (or even 140).

Like most things in life, it's a trade-off -- neither decision is right or wrong.

jim (tired of a simple decision becoming a running gunfight... Description: http://forum.miata.net/vb/images/smilies/frown.gif)

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Description: Old 25th January 2011, 15:21

  #62

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Quote:

Originally Posted by Jim Boemler Description: View Post

If the notion of trading a little gas mileage for more diff protection bothers you, by all means buy the 90. If the notion of trading a little diff protection for some gas mileage bothers you, buy the 110 (or even 140).

Like most things in life, it's a trade-off -- neither decision is right or wrong.

jim (tired of a simple decision becoming a running gunfight... 
Description: http://forum.miata.net/vb/images/smilies/frown.gif)

The annoying thing about this argument is that neither side really has any data. Neither side has any used oil analysis to prove that either oil is better or worse. It really boils down to one question, do you think you're more clever than the engineer who designed the car?

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Description: Old 25th January 2011, 17:10

  #63

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Not quite, Raven. The question is "Do you have the same priorities as the manufacturer?" It's not that you or they "know more". The manufacturer has a lot of criteria that you don't -- cost, emissions, mileage, corporate partnerships, etc. It's legitimate to think of the manufacturers recommendations as "minimums", and sometimes they're even better than minimum, but their goal isn't to recommend "the best" for you -- that's your job.

jim

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Description: Old 25th January 2011, 17:31

  #64

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Well said JB.

The great thing is that no one can make anyone else put anything in their car. 

Follow the owner's manual. Don't change it all. Drain it, run it through a coffee filter and put it back. Whatever puts a shine on your armor. You can follow the advice of the butcher, the baker or the candlestick maker. 

Me personally? I'd follow the advice of the guy who builds rearends for a living.

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Description: Old 25th January 2011, 19:40

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Quote:

Originally Posted by mx5mia Description: View Post

Bimmer... I wanted to comment on the 75w-90NS you have in the tranny. 

So if you are using the 75w-90NS in a transaxle, then you are OK...

I'm afraid that this wasn't for a Miata, it was for my '02 Subaru Impreza (I think I mentioned this above somewhere).

FWIW, Redline's 75w90NS (and one quart of the Redline's Lightweight Shockproof "Smurf Blood") is highly praised on the Subaru forums for the manual transaxles, and it made shifting much easier in my car.

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Description: Old 25th January 2011, 19:47

  #66

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well...


Quote:

Originally Posted by Raven18940 Description: View Post

The annoying thing about this argument is that neither side really has any data. Neither side has any used oil analysis to prove that either oil is better or worse. It really boils down to one question, do you think you're more clever than the engineer who designed the car?

i have one, just haven't sent it in yet, 60k on my 02LS. hopefully go out in the mail this week to blackstone.

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Description: Old 25th January 2011, 20:02

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Quote:

Originally Posted by Raven18940 Description: View Post

Neither side has any used oil analysis to prove that either oil is better or worse.

It wouldn't really prove anything if we did, either...

You'd need dozens is not hundreds of UOAs to come up with statistically significant conclusions. 

If you're trying to decide between 75w90 and 75w110, then the margins of errors on UOAs are too big, and the other variables like manufacturing tolerances in differentials, different brands of oil, and different driving styles, are virtually insurmountable. 

For example, Driver A's differential might show a lot more wear than Driver B's, even if they use the same oil. 

Or a sample of Brand A 75w90 after 30,000 miles might show a lot less wear than a sample of Brand B 75w90. 

Or a sample from a differential made on a Monday might show a lot more wear elements than a differential made on a Tuesday, even if everything else (weight and brand of oil, driving style) were the exactly the same. 

Or you could send the same exact sample to several labs and have results that vary 10-20%. Really. 

So, pick whatever you guess will work best. Or do whatever your brother-in-law recommends (or the opposite). Or whatever Mazda says. Or whatever Puddy says. Or whatever Amsoil says. I don't know...

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Description: Old 25th January 2011, 20:06

  #68

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Quote:

Originally Posted by cheetahdriver Description: View Post

i have one, just haven't sent it in yet, 60k on my 02LS. hopefully go out in the mail this week to blackstone.

Despite what I just wrote, your viscosity numbers would be interesting to see. 

I wonder if a 75w90 gear oil is stable, or whether shears down to 85 (less than 13.5) or even 80 weight (less than 11.0) over 60,000 miles... 

If 75w90s are shearing down to less than 90-weight, then that would be a big argument in favor of starting with 75w110, though I'd be really surprised if synthetic gear oils are losing much viscosity.

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Description: Old 25th January 2011, 20:33

  #69

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yep..


Quote:

Originally Posted by Bimmer Description: View Post

Despite what I just wrote, your viscosity numbers would be interesting to see. 

I wonder if a 75w90 gear oil is stable, or whether shears down to 85 (less than 13.5) or even 80 weight (less than 11.0) over 60,000 miles... 

If 75w90s are shearing down to less than 90-weight, then that would be a big argument in favor of starting with 75w110, though I'd be really surprised if synthetic gear oils are losing much viscosity.

i agree with every statement in your post...

just as a point of reference, here is a 100k/10yr UOA out of my tundra (has the aftermarket TRD Limited Slip diff). 

http://www.bobistheoilguy.com/forums...64685&page=all

there is a comment that it sheared to an 80wt in the thread, but that is in error, at 16.16cSt, it is still a very solid 90wt. if 100k in a truck diff used for towing with a V8 didn't shear it...probably ain't gonna shear. note the comments by both Doug Hillary and Molakule in the thread.

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Description: Old 25th January 2011, 21:44

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Quote:

Originally Posted by Bimmer Description: View Post

It wouldn't really prove anything if we did, either...

You'd need dozens is not hundreds of UOAs to come up with statistically significant conclusions. 

If you're trying to decide between 75w90 and 75w110, then the margins of errors on UOAs are too big, and the other variables like manufacturing tolerances in differentials, different brands of oil, and different driving styles, are virtually insurmountable. 

For example, Driver A's differential might show a lot more wear than Driver B's, even if they use the same oil. 

Or a sample of Brand A 75w90 after 30,000 miles might show a lot less wear than a sample of Brand B 75w90. 

Or a sample from a differential made on a Monday might show a lot more wear elements than a differential made on a Tuesday, even if everything else (weight and brand of oil, driving style) were the exactly the same. 

Or you could send the same exact sample to several labs and have results that vary 10-20%. Really. 

So, pick whatever you guess will work best. Or do whatever your brother-in-law recommends (or the opposite). Or whatever Mazda says. Or whatever Puddy says. Or whatever Amsoil says. I don't know...

You have excellent points. This is why I side with Mazda though, because the stress testing a modern car goes through before it's sold is beyond anything they'll see in their entire lifetime. So whatever the recommend is at the very least going to be pretty good. 

Then I take those specs and replace it with fully synthetic so the oil will perform even better. Description: http://forum.miata.net/vb/images/smilies/tongue.gif

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Description: Old 25th January 2011, 22:59

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Quote:

Originally Posted by Raven18940 Description: View Post

I side with Mazda though, because the stress testing a modern car goes through before it's sold is beyond anything they'll see in their entire lifetime. So whatever the recommend is at the very least going to be pretty good. 

Then I take those specs and replace it with fully synthetic so the oil will perform even better.

Just to be clear, though... you wouldn't wait until 60,000 miles to change your differential oil!

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Description: Old 26th January 2011, 11:00

  #72

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Does anyone but Amsoil market a 75W110 GL5? 

I did a google shopping search and found lots of 75W90 and 80W90, and a few 75W140s. But no one else seems to sell a 75W110. I'm more than a little suspicious of anything Amsoil claims.

It seems to me that if 75W110 was really needed in modern differentials, all the oil vendors would be supplying it, and most (if not all) manufacturers would recommend it. Am I missing something?

I don't claim to be an expert, but I have to think that if manufacturers were recommending 75W110 oils then oil manufacturers would be supplying those oils more widely. And it seems unlikely to me that manufacturers would continue to recommend 90W oil if it were insufficient.

I suspect that the actual viscosity of the various grades have gotten thinner for the same reasons that engine oils have gotten thinner: improved tolerances and energy savings. But I doubt seriously that manufacturers who are providing warranties of up to 100,000 miles on the drive train would be recommending an oil that was inadequate to the job.

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Description: Old 26th January 2011, 11:29

  #73

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Quote:

Originally Posted by meyerweb Description: View Post

Does anyone but Amsoil market a 75W110 GL5? ....

IIRC I found an outfit called Coastal, but that was it.

I agree that if it was being recommended by the car makers or diff makers then the majors would be marketing it.

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Description: Old 26th January 2011, 13:01

  #74

 

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Quote:

Originally Posted by Bimmer Description: View Post

Just to be clear, though... you wouldn't wait until 60,000 miles to change your differential oil!

If I wasn't going to swap it for synthetic I might. 

4 years ago I'd be gun ho about this sort of thing. Now I'm out of college (no time) and no longer have a garage (no space). My maintenance enthusiasm has diminished considerably. I really just do what's required, not what I think I should do.

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Description: Old 27th January 2011, 18:21

  #75

 

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The somewhat wide range of cst for the new 75w90 spec & the fact that manufacturers aren't revising their recommended oils en masse suggests to me the following:

* it's not terribly important to longevity

* the oil company cst average for 75w-90 hasn't changed much over the years, despite the official spec change

I mean, if diff technology hasn't advance that much over the years then it shouldn't be too picky about what kind of lube it uses right? I remember hearing about the 24hours of lemons people's curse Mercedes 300D diesel that was selected for destruction by putting anything whatsoever in the engine oil then blowing the motor. People put puke, piss, beer, whiskey, and countless other fluids in there... the motor would not fail. In fact they decided to let the car run with those fluids inside and the car actually completed the race. As much as I like good clean fluids running in my car, I'm not convinced that it makes a huge difference. I mean, I've never (first hand) heard of a failed differential on a street car in my entire life.

http://jalopnik.com/5289202/so-whats...curse-business

 

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Description: Old 27th January 2011, 18:32

  #76

 

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Quote:

Originally Posted by Old Crow Whiskey Description: View Post

... I mean, I've never (first hand) heard of a failed differential on a street car in my entire life. ...

A couple of years ago an NC diff locked up solid. Turned out they forgot to put any oil in at the factory. Description: http://forum.miata.net/vb/images/smilies/eek.gif

At least that's what was posted. 

So apparently oil of some type helps. Description: http://forum.miata.net/vb/images/smilies/wink.gif

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Description: Old 27th January 2011, 20:56

  #77

 

Bimmer

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Originally Posted by Old Crow Whiskey Description: View Post

I remember hearing about the 24hours of lemons people's curse Mercedes 300D diesel that was selected for destruction by putting anything whatsoever in the engine oil then blowing the motor. People put puke, piss, beer, whiskey, and countless other fluids in there... the motor would not fail.

Just to keep you honest... I read the link you sent (and I've read the articles on the 24 Hours of LeMons in C&D). 

They put all that crap in the THROTTLE BODY of the Benz, not in the engine oil. 

No surprise it survived: diesels will continue to run on just about anything... 


The guys on the gun forums go nuts chasing their tails, trying to figure out the best lubricants. I gave up and now use Mobil 1 20w-50. 

Rather famously, one AR-15 guru sustainably fired his rifle after lubricating it liberally with a feminine hygiene product. Really. 

Of course, I'm not recommending filling your differential with Vagisil (75w-90 is cheaper).

 

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Description: Old 27th January 2011, 23:21

  #78

 

humfrz

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Originally Posted by Old Crow Whiskey Description: View Post

........I mean, I've never (first hand) heard of a failed differential on a street car in my entire life......

Interesting point.....me either (at least not because of the choice of lubricant)......Description: http://forum.miata.net/vb/images/smilies/wink.gif

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Description: Old 28th January 2011, 10:00

  #79

Raven18940

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Originally Posted by Bimmer Description: View Post

The guys on the gun forums go nuts chasing their tails, trying to figure out the best lubricants. I gave up and now use Mobil 1 20w-50.

That's a different situation. The gun manufacturers provide no specs on the correct oil, just that you should use their proprietary lube.

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Description: Old 28th January 2011, 11:13

  #80

arejohn

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What's your definition of fail. Mine was replaced because of a whine. Stayed quiet for a few weeks and now I think it's noisy again. Not sure because there are so many other noises.

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Description: Old 28th January 2011, 12:21

  #81

Raven18940

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How loud of a whine? I've never had a diff or trans that was completely quiet. Even my brand new 6 spd makes a low volume whine when I step on it.

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Description: Old 31st January 2011, 08:54

  #82

cheetahdriver

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i have seen numerous diff failures...


mostly consisting of tooth failures due to improper application of power done repeatedly (can you say redline a V8 and drop the clutch?). i have also seen wear failures, but mostly on Class8 trucks with 300k+ on the diffs. that's where using the wrong lubricant can get you in serious trouble. a good synthetic lubricant can go 80 to 100k in a well designed street diff. it can go maybe 20k in something like an S2000 which has more HP than a miata and a diff oil capacity that is measured in ounces.

application, application, application. 

for the miata, a good synthetic in the diff will lower temps, and give you some small fractional HP increase (which you will never feel). it will do well for 80-100k and be in various stages of failure (the oil, not the diff) for the next 50k. a good dino oil will do well for 60k and be serious toast at 100k. i like not worrying about it.

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Description: Old 1st February 2011, 00:39

  #83

RubyDoo

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110 has been so hard to find that I decided to go with 90, figuring it's better for my cold-weather driving anyway. I'll change it more often. 

And people, please let's quit quoting the Mazda recommendations like they are carved in stone by a burning bush. Again, remember that they also recommend a tranny oil that we have proven again and again does not work, and there is that post above where Mazda sent the guy to the totally wrong page in the manual.

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Description: Old 1st February 2011, 03:35

  #84

Jim Boemler

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Originally Posted by RubyDoo Description: View Post

And people, please let's quit quoting the Mazda recommendations like they are carved in stone by a burning bush.

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Description: Old 1st February 2011, 08:05

  #85

wooo

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Originally Posted by RubyDoo Description: View Post

110 has been so hard to find that ... 

And people, please let's quit quoting the Mazda recommendations like they are carved in stone by a burning bush. ...

At least Mazda didn't recommend an oil that's "so hard to find". Description: http://forum.miata.net/vb/images/smilies/rolleyes.gif

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Description: Old 1st February 2011, 08:47

  #86

Gear Poet

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That's quite a 180, and without even a fishtail.... To go from calling one opinion-ator a god whose authority cannot be challenged, to recommending that we topple stone idols and douse burning bushes erected by the god-like car-maker. 

In this thread, being a graduate of a defensive rhetoric school of driving is good. 

I'm not sure I've ever seen such passionate argument over an issue with so little practical difference. 75w-90 or 75w-110, etc., in a Miata? A street Miata?? The free-haulers who truck 20K+ loads 60K+ miles per year in Dodge/Cummins diesel pickups don't tussle so hard over diff lubes in certain other forums I frequent.... But they have had fun lurking in this thread, and wish me to thank you all. Description: http://forum.miata.net/vb/images/smilies/wink.gif

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Description: Old 1st February 2011, 09:11

  #87

RubyDoo

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That's quite a 180, and without even a fishtail....

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I guess my avatar is a metaphor as much as it is a real-world icon.

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Description: Old 1st February 2011, 13:17

  #88

Raven18940

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Originally Posted by RubyDoo Description: View Post

Again, remember that they also recommend a tranny oil that we have proven again and again does not work, and there is that post above where Mazda sent the guy to the totally wrong page in the manual.

I think the real issue with GL-5 in the trans is not that it's GL-5 but that most GL-5 gear oil comes with limited slip additive, which makes synchros not work so well. 

Also, I wasn't really expecting the tech support line to give me a real answer. Tech support isn't staffed with engineers.

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Description: Old 1st February 2011, 13:34

  #89

wooo

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Originally Posted by Raven18940 Description: View Post

I think the real issue with GL-5 in the trans is not that it's GL-5 but that most GL-5 gear oil comes with limited slip additive, which makes synchros not work so well. ....

Don't forget those persistent EP additives.

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