scottyp99

You are correct, and for what it's worth, concerning his '81, I would use whatever the service manual said to use. If you don't have a service manual, get one. Haynes and Chilton both make a good one for our cars.

I just mentioned my brother's '97 because some folks seemed incredulous about ATF in manual transmissions, to show that, yes, there are some modern transmissions that use ATF.


Scott

C66 Racing

Not trying to inflame the debate, but concur that there are many manuals that use ATF including C5 and C6 Corvette Tremec manuals (my 02 Z06 uses an ATF for the six speed).

For the OP, this is AMSOIL's recommendation for your manual:
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 (Product Code SVGQT)

Interestingly, same fluid I use in my diff.

Faster Rat

I went with what the poster originally said too. That is why I spoke about a specific lubricant that I used in my car, that so happens to be a 90W gear oil and is colored red...like ATFs.

I know enough about manual trannys to know that a person should use what the manufacturer specifies. The last manual tranny car that I owned or worked on, prior to this vette, was a 1966 GTO that I bought in 1968. Pardon me.

Capt. Shark

first I thought WTH?

...Roger...

It's actually in the front.

tnovot

Exactly!!!
Terry

jb78L-82

I refer to my original post on page 1:

"I was aware that some newer manual transmissions used automatic fluid like the 4+3 in the C4's as well as my 1988 Mustang 5.0 manual but have never seen it specified for older 4 speeds like the M22/M21/Borg Warner Super T-10's or in any C3. So are you saying that there are C3 manual transmission cars that had automatic fluid filled from the Factory?"


Like I said , never heard of a C3 manual transmission car ever having ATF fluid in the gear box!!!

babbah

Sta Lube GL-4 - My 44 year old Munice - never touched - still flawless operation - Running this in it since car was new.......

69 Chevy

This is what I put in my '69 M21:

http://www.jegs.com/i/Richmond-Gear/...oductId=753497

MelWff

Thank you Roger, so it's not ATF for this specific application.

tnovot

Prior to my C3, I had an '84 with the 4+3 and to the best of my recollection, only the OD unit (basically a powerglide trans) used ATF but the 4 speed box itself used regular gear lube.
Terry

jb78L-82

yes you are correct-not a good example from me! The C3 manuals never used ATF fluid as far as I know-just use a Gl 5 fluid and call it a day!

...Roger...

Not according to the 81 Corvette shop manual,but that's not to say that ATF is not OK or even better in some aspects.
Is using ATF an upgrade ? Most of us certainly don't have a problem upgrading cam shafts,heads,carbs and etc.
I think fuel savings and probably more HP to the rear wheels would be important to some,but being safe with the old heavier lube might be for others.

mrvette

Exactly, and my '72 here had a muncie in it, when I got it the thing shifted like a damn old school bus, hard and clunky even when hot, compared to newer cars.....so I changed fluid to 30W synthetic engine oil....it shifted like a new car then, slick as snot on a doorknob.... ran for two years that way, daily driven trip to Florida and back from Maryland, never a issue....

swapped in a OD auto for the ODrive....here, as speeds/distances are much greater than the DC region....

jb78L-82

I had the same issues 20 years ago in my 4 speed-notchy when hot, down right stiff and resistant to shifting when cold, etc-changed to Amsoil gear oil and most recently to mobil 1 75W-90 full synthetic gear oil GL-5-never have had an issue since! My experience is that using a quality synthetic gear oil is all you need to do-no need for ATF/motor oils etc. I just changed this weekend the rear diff fluid on my 1994 mustang GT to mobil 1 75W-90 gear oil after 17 years (I know I should have done it much sooner!-26,000 miles on the car).

...Roger...

I was told by a lubrication engineer that the unlike metals (non-ferrous and the ferrous)need a special lubricant so the braking action takes place in the synchro. Some lubes and maybe worn out or dirty lubes hinder the braking action needed to match gear speeds and shift smoothly.

Mike 1959

Is it true that GL-5 fluid is not compatible with the synchros in a (old) 1959 T 10 manual transmission. That you must use GL-4 fluid. Because the shifting from 1st to 2nd was getting rough on my just rebuild transmission last year, I changed from a 90w GL-5 fluid to AC Delco Manual transmission fluid SAE 75W-85 G-4. The shifting got better last year, just got it back out this year and now I have a bearing whine when I down shift for braking. The AC Delco fluid is thin like ATF, not thick like the old 90w fluid.

dugsgms74

Just my .02 worth. Beware of using GL-5 in older transmissions unless specified by the factory. It has a higher sulphur content that not only inhibits the sychros from working but also degrades yellow metal parts over time. I have a 06 pontiac solstice that asked for GL-4, I put in GL-5 and it didnt shift for ****, had to get the correct fluid from GM to fix the problem. I need to change the fluid in my 68 but am still looking for a local source for GL-4.

Torqued Off

Notice the guy who called everyone a moron is silent now that the Service Manual was shown.

Yes, people make upgrades all across our cars, but the fact that someone on this forum says its a good idea in no way makes it so. This forum, like all forums, have so called experts, and usually they are the ones calling everyone else morons. Pretty typical.

Marlin

Amazon has GL-4 75W-90 for manual trans.


That's what I bought but there are a couple others as well.