Another manual transmission question.

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aquariuscsm

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Well,I tried a 2 quart 75W85 GL4/1 quart ATF mix. It shifts smooth as silk when it`s cold,but it gets notchy and the 1st to 2nd gear grind comes back just like before once it`s good and hot. What could possibly make the shifting degrade when it gets hot??????

Would the thickest gear oil money can buy be the best option? Maybe taking it very easy when it`s cold,then once hot the thicker fluid helping the gears get the cushioning they maybe need?

Here`s the gear oils I saw while touring the auto parts stores today. What`s everyone`s input:

Valvoline 75W90 (GL5/MT-1.........what`s MT-1 rating?)
Mobil 1 75W90 (GL5)
Coastal 85W90 (GL3 GL4 GL5 MT-1)
Redline MT90 (GL4)

I`ve read about Pennzoil 85W90 GL4,but I can`t find it anywhere.

I also have my 4 quart emergency stash of Nissan 75W89 GL4.

The service manager at the Nissan dealer said GL5 oils won`t hurt the tranny and that it`s basically an old wives tale.

Ok BITOG experts........help a brutha out :^)
 
*correction on the Pennzoil*

Looks like they make a synth Gear Plus 75W90 and a dino 80W90 both in GL4. Anyone know where to get it? I`ve read good stuff about it on some other car forums.
 
Sorry,another typo. I`ve been up since 4am:

Nissan 75W89 GL4 should be *Nissan 75W85 GL4*.
 
Here`s something I`ve never heard before.........I was just searching/researching on a Nissan Z forum,and some of the members use 20W50 and 15W50 motor oils in their manual trannies and love the results.

This is a new one on me. What`s the difference between a thick motor oil (aka 20W50) and a gear oil ala 75W90?
 
Originally Posted By: aquariuscsm

What`s the difference between a thick motor oil (aka 20W50) and a gear oil ala 75W90?


http://www.infineum.com/information/api-viscosity-2004.html

http://www.lubrizol.com/products/automotive-gear-oil/J306.asp

The above will help when comparing viscosities.

The additives are all different. Gear oils have more EP additives, and designed to protect gears in extremely high pressure, inevitable contact situations - typically by forming FeSx type compounds....motor oils have more temp/time activated AW additives and whole bevy of other additives to deal with fuel and different forms of scunge and dirt.

In the old days motor oil was a pretty good substitute for lighter gear oils, but it seems the two lubricants are further apart than at any time in auto history. Not saying it won't work, though.

So you gave up on trying MTF/MTG?
 
While my truck is far removed from your Z it's manual tranny reacts the same way to "thinner" tranny fluid, It hates and shifts poorly when it warms up and is horrible in the summer. Originally spec'd and factory filled with Mercon it was torture to drive in the warm/hot weather. Molakule's synthetic Synchromesh fluid really helped but it still balked more so when it was warm/hot outside. But when it's freezing it shifts like a hot knife in butter. I'm hesitant to go thicker for fear of starving the gears of lubrication since it was originally spec'd for ATF. I changed to some new "donated" RP Synchromesh fluid. It's thinner but shifts the same as the thicker Molakule SF fluid. I think the tranny just stinks no matter what fluid you put in.

Amsoil spec's their European 5W-40 engine oil for the manual tranny in my 1996 Contour. It came from the factory with Mercon ATF. Ford respec'd it for their "Gold" tranny fluid, a 75W-90 synthetic, which I used. I recently used the RP Synchromesh and it shifts just fine. It shifted just fine with the ATF but I understand that ATF does not have the AW & EP additives that a manual tranny should use for a long life. Saying that I'm not too sure about using engine oil. I don't think it contains the AW & EP additives either
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Whimsey
 
Sorry Pab,I was sooooooo tired when I posted last night that I forgot to mention Amsoil in the list of fluids I`m curious about. There`s a hot rod shop here in town that carries their motor oil,but not their gear oils,but he can order them for me. Would you recommend I use the thickest they make?............the MTG,right?
 
Also,what is MT-1 rating? Amsoil,Castrol,Valvoline,and Mobil both have 80W90 gear oils that say GL5/MT-1 and can be used in manual trannies.

Also,what about the GL5 being harmful? I keep seeing here and on different forums that it`s basically old news and an urban legend,per se.
 
I dont know what truck you have but in my old ranger, the fords spec'd ATF because of the needle bearings they used throughout the transmission instead of roller bearings.... You're not going to "starve" the gears with gear oil, they're probably gonna love it. You wont be properly lubricating/cooling all the bearings in it if you run anything thicker than ATF though. That was the common death to the ford/mazda M5OD's The factory specd the fluid for a reason. I got over 250'000 out of my ranger's M5OD before I sold it, and it had M1 ATF in it since 80,000 As soon as I put the M1 in it, it went silent and shifted better. I beleive it was the factory fill I drained out at 80,000 as it was disgusting and whining in 5th gear
 
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Originally Posted By: aquariuscsm
Sorry Pab,I was sooooooo tired when I posted last night that I forgot to mention Amsoil in the list of fluids I`m curious about. There`s a hot rod shop here in town that carries their motor oil,but not their gear oils,but he can order them for me. Would you recommend I use the thickest they make?............the MTG,right?


MTG is on "lighter" side of the 90 range for a 75W-90. It is a GL-4. It's what is recommended by Amsoil. But indeed MTG at 14.7 cSt is higher viscosity than MTF.

Amsoil MTG

Viscosity Ranges for Gear Oils

First find out what he will charge you, before not ordering from a BITOG site sponsor.
 
Originally Posted By: aquariuscsm
Also,what is MT-1 rating? Amsoil,Castrol,Valvoline,and Mobil both have 80W90 gear oils that say GL5/MT-1 and can be used in manual trannies.

Also,what about the GL5 being harmful? I keep seeing here and on different forums that it`s basically old news and an urban legend,per se.


MT-1 is an older (I think even non-synchro) MT truck gear oil spec. Search around on the API site.

I don't think a modern synthetic GL-5 will hurt anything, but I'm not sure it will give you the best shifting.
 
I drained the Nissan MTF/ATF mix today and re-filled with 3 quarts RL MTL and 1/4 quart RL MT-90 (I had it leftover from awhile back). The tranny holds 3 quarts basically but the entire 1/4 quart MT-90 went in before it began to drip out of the fill hole.

Test drive wasn`t notchy at all. Shifts felt really smooth and cushioned. MUCH more cushioned than the MTF/ATF mix. The MTL feels a bit more thick and slippery in your fingers than the Nissan MTF I noticed.

*keeping fingers crossed*
 
Drove around today with the MTL/MT-90 mix and still no notchy shifting or gear grind/crunch. Also slides into 1st and reverse from a standstill with awesome precision and cushioning.

Maybe these trannies just need the right cocktail of fluids? Lord I hope so!
 
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