manual transmission lube question

[QuickSilver]

my car is a 2007 hyundai elantra. the specs call for 75w-85 GL-4 gear oil. Thats what the OEM spec is. I would like to use 75w-90 GL4 Manual Transaxle fluid from Amsoil.

Is the difference of 75w-90(Amsoil) and 75w-85 (OEM) going to make a huge difference? They are both Synthetic and both GL-4.

 

[Pablo]

Amsoil MTG at 14.7 cSt viscosity misses an 85 (<13.5) by 1.2 cSt. I doubt you'll notice a difference. In fact I would bet some cash you won't notice....I think what they don't want in there by calling out 75W-85 GL-4 is a killer high viscosity old spec 75W-90 GL-5. (vis of 23.9!)

 

[Bror Jace]

Pablo, Some Nissans and some Hyundais share transmissions (built by Nissan?). Older Nissan transmissions spec'd 75W-90 oil. I thought I read on here that Nissan tried to address complaints about shift quality in the vehicles by recommending a slightly thinner oil for their transmissions ... which they spec as a 75W-85. The transmission tolerances, clearances (supposedly) did not change much.

The Amsoil 75W-90 might be fine ... for Virginia. But if he was further north, I'd go lighter, not heavier than OEM spec. Maybe a mix of MTG and Sever Gear 75W-90?

 

[Pablo]

Originally Posted By: Bror Jace
Pablo, Some Nissans and some Hyundais share transmissions (built by Nissan?). Older Nissan transmissions spec'd 75W-90 oil. I thought I read on here that Nissan tried to address complaints about shift quality in the vehicles by recommending a slightly thinner oil for their transmissions ... which they spec as a 75W-85. The transmission tolerances, clearances (supposedly) did not change much.


Kinda what I was saying - seems like they are steering the consumer away from the old high viscosity 90's. Which MTG isn't, it's near the bottom of the viscosity range.

Originally Posted By: Bror Jace
The Amsoil 75W-90 might be fine ... for Virginia. But if he was further north, I'd go lighter, not heavier than OEM spec. Maybe a mix of MTG and Sever Gear 75W-90?

Actually that would make the viscosity even higher. MTG = 14.7, SVG is 16.7 cSt. If you want to cut the MTG viscosity down, it's OK to use the MTF. It's what I do in my Volvo, works great.

 

[aquariuscsm]

Nissan doesn`t actually make the transmissions (so I`ve heard). In the 80s they used BorgWarner/Tremec T5`s in the Z31`s.

Unfortunately they`re not using the Tremec T5`s anymore. There`s a ton of speculation on who`s making the manual transmissions for the Z32`s and Z33`s now,but Nissan won`t reveal it because of so many problems with them.

I`ve tried several gear oils:

RP Max Gear 75W90 (this one was the worst,probably because it`s too thick for proper synchro engagement. Every gear shift would crunch/grind. The GL5 rating also made me uneasy. I`d feel more comfortable with a GL4 only rating).

RL MT90 (this one was the 2nd worst,I`m guessing the thickness as well).

Nissan MTF 75W85 (this one was actually really good,but still gave me a bit of gear crunch if I didn`t shift slow enough).

RL MTL (this fluid ROCKS!!!!!!!!! Shifting is smooth as silk! No issues whatsoever. Shifts flawlessly when ice cold and even better when it`s hot).

 

[wantin150]

50/50 (or 60/40) mix of Redline MTL and MT90.

 

[double vanos]

aquariuscsm...that is what I plan to do with my Mazdaspeed 3 - straight Redline MTL instead of the 75/90 Mazda wants.

Am currently running 50/50 mix of MTL and MT90 and it's pretty good but there's still that occasional cold temp grind. This is VERBOTEN!!

MTL all the way next oil change!

 

[aquariuscsm]

If your manual transmission is anything like mine (which also specs a 75W90 via FSM),it will love the MTL. One of the things I noticed with the 75W90,is that the transmission became very stiff and notchy once it was good and hot (complaints made my alot of Z32 and Z33 owners). With the MTL,the more hot the transmission gets,the smoother the shifts become. Once it`s good and hot,I can literally shift through all the gears with my pinky finger......it`s honestly that smooth and easy.

When you decide to install the MTL,give it a few weeks of driving. I definitely noticed a difference upon first test drive,but the more I drive,the better the shifting action is becoming. Input shaft bearing noise is virtually gone also.

I think Redline got manual transmission fluid right on when they made the MTL.

 

[Bror Jace]

I said: " Maybe a mix of MTG and Severe Gear 75W-90?"

Pablo: "Actually that would make the viscosity even higher. MTG = 14.7, SVG is 16.7 cSt. If you want to cut the MTG viscosity down, it's OK to use the MTF."

Oops, I got my Amsoil products mixed up. I was thinking of a blend of the two synchro fluids.

auquariuscsm: "If your manual transmission is anything like mine (which also specs a 75W90 via FSM), it will love the MTL."

I would caution people not to run straight Red Line MTL in a transmission calling for a 75W-85. It's significantly lighter and there could be long-term consequences. A member here who drives a Mazda Miata thinks a very short stint of Red Line MTL did noticeable damage to his transmission (which called for a 75W-90). He switched back to 75W-90 and shifting did not return to it's former quality.

But, it's your ride so be my guest.

 

[mjoekingz28]

so, is it okay to run a thicker oil than is called for but is not good to run a bit thinner

70w80 MTL
75w85 Factory spec
80w90 MT90

In my last car that specified ATF for the 5spd, I used MTL and shifted like butter.

 

[mechtech2]

Thicker is not necessarily better.
Their are thinner gear lubes that protect better than some low end thick ones.

 

[unDummy]

Most 90wt's will shear into an 85 anyway. Since the Amsoil is a full synthetic, cold weather performance should be good enough with the Amsoil MTG. But, you can always thin it out a little using the MTF.

You can go a little thicker or thinner if needed for climate or other issues. I prefer to use the thickest gear oil that I can get away with for protection. Quality transmission rebuilers and supply of parts for most manuals are difficult to find.

Shift quality/MPG will improve with thinner gear oils. Dropping down a couple CSTs shouldn't be an issue with ANY of the quality boutique gear oils. A drastic drop should be avoided.
A used oil analysis can be used to determine if the fluid is too thin.

Besides the Ams, RedL, RylPurp, Neo, Torco, Silkolene, Motul..... boutique fluids, there are several OEM gear oils that work just as well. Most Nissan dealers stock the 75w85. Ford has a 75w90. Hondacura has the 30wt(~75w80ish)fluid.