Hey guys,

I have a spare 79 Transmission or three,and I am replacing the blown 79 transmission in my 74 RX4. I found a box with 5-6 quarts of 75W90 Amsoil in it today,and was wondering if I bought it for my rear axle in the 79,or the transmission way back when.

Under the hood of the RX-7 it calls for either GL-4,or GL-5 and SAE 80,or SAE 90 depending on the temps you operate the car in. Will this 75W90 I have be the right stuff,or is it only for rear axles? When I went to the local Advance Auto they had the same 75W80,or 90,but I didn't see anything that was listed as SAE90 gear oil. Is this just something that has a new designation,and therefore the same stuff,or do I need to find this SAE90 oil?

Any help would be appreciated.

Chris

 

I would think that you'd probably be okay with it.

I use a 50/50 mix of gear lube and ATF, which has always worked great for me.

 

That's what I've been using for last 4 yrs - no probs, in both diff and tranny...

Stu Aull
80GS
Alaska

 

The 75W90 Stu,or the 50/50 gear lube,and ATF?

 

50/50 75W90 and ATF is awesome! Learned that from kentetsu on here and it has worked great for me, smoothed out shifting a little bit

 

The idea (which I got from a book on racing Datsuns) is that the ATF provides plenty of lube, but also has a shitload of detergents which keeps gunk from building up in the synchros (and cleans out whatever is already in there).

This provides smoother, quicker shifting and since there's reduced buildup, should keep the tranny alive much longer.

I've been using this combo for a couple of decades, in about a dozen different vehicles. It always improves the shifting and I've never had any sort of tranny issues, ever.

 

Sorry!
Straight Redline, tho Kentetsu's ATF idea is interesting......

Stu Aull
80GS w redLine
Alaska