(I tried searching for this and transmission fluild but did not get any info I needed, so I'm posting.)

For all of you who has replaced your 6MT tranny fluid or know about this subject:

1) Is it OK to use API GL-5 75w-90 on the tranny and differential? (Mobil 1 sys)

2) What is the difference between API GL-4 and GL-5?

The instruction manual says API GL-4 75w-85/90 for the tranny and API GL-5 80w-90 for the differential, but I could not find any GL-4

Need help quick...

 

I use synthetic 75w-90 GL-5 in the tranny and differential. I swapped out the tranny oil when the car was brand new and haven't had any issues.... no grinding, no notchiness....perfect.

 

Thanks g356gear.

I did more search for Gl-4/5 and know the difference between them.

 

A lot of people said GL5 is corrosive to the syncros and not to use that rating for tranny oil. I also had a hard time finding GL4 tranny oil so I went with GL5 Royal Purple instead, both tranny and differential. Tranny *feel* a bit more smooth and less notchy, but not by much.

 

so what is the difference between them??

 

Based on what I've read, API GL-5 has special additives that allow it to outperform GL-4 (not sure in heat/friction or etc), but because of the added chemicals, it is NOT good for transmissions which use copper synchros -- such as the Z/G's. Doing so will cause premature corrotion in the "yellow metal."

The dealer's OEM tranny fluid costs $17 a qt. and the Z's tranny uses a few qts. (not exactly sure how many).

 

This thread may help.

 

Thanks a lot Monsta, that really made everything much clearer!! You da man.

 

I'm using Amsoil GL4.