My '04 GTO uses ATF in the manual tranny. I would run whatever the owner's manual says to.

Rob

 

The problem with GL-5 in a GL-4 recommended tranny is the GL-5 is too "slippery" to allow the synchros to operate correctly, resulting (possibly) in issues with the gears "chinking". GL-4 should be used. If the stuff you're using says GL-4/5/whatever, you should be good to go.

 

can you guys recommend a t-case rebuild kit? my seals are leaking and i have some play where the rear driveshaft enters the t-case. how difficult is it to take it off the tranny, and is it something i can accomplish myself?

 

There's definitely something to it.

A while back I started having shifting problems. I'm going to leave out the details for being lazy, but suffice it to say I was almost positive the transmission was going. Scary. So, I put in a new shifter seat bushing. That helped, but did not alleviate the sticky shifting particularly downshifting from 3rd to 2nd. So, I put GL-4 (MT-90) in and....viola!....any and all problems are gone and have been for quite some time.

Maybe GL-5 won't corrode the brass synchros, but as far as I'm concerned not having the gears stick and/or grind totally justifies any GL-4 > GL-5 arguement....as far as the 5-spd goes.

 

I just cut and pasted this from the Automotive Repair Reference Center Database. These are specs for a 1992 4-runner with a 3.0L V6.

Transfer Case
FLUID RECOMMENDATIONS
Trucks and 4Runner's w/MT — multipurpose gear oil API GL-3, GL–4 or GL–5; SAE 75W–90 or 80W–90
Trucks and 4Runner's w/AT — ATF DEXRON® II or its superceding fluid type
Land Cruiser — multipurpose gear oil API GL–4 or GL–5; SAE 90W.

Manual Transmission
FLUID RECOMMENDATIONS
All vehicles use a multipurpose gear oil. The recommended types are: API GL-3, GL–4 or GL–5 with the viscosity SAE 75W–90 or 80W–90.

Automatic Transmission
FLUID RECOMMENDATIONS
All automatic transmissions covered in this manual use DEXRON® II or its superceding fluid type.

This database is what colleges use to teach people how to work on cars. You can find almost anything on here. There are benifits of being a college student.

 

I have the book and it says the same thing. Confused me as well, the owners manual that came with my 91 said it takes 75w90 (I think that's it) gear oil. Either way, the books wrong, it takes gear oil.

 

I just checked my 93 pickup 5spd t-case and it's ATF. I have no idea how old it is as I've never changed it. I guess I'll replace it with some of the mt90 I got for the tranny.