Diff Fluids??
 

Hey, I need some help on what kind of Diff Fluid I should use. I have LSD and it's a 5 speed. What is GL-4, -5? Can I use Royal Purple Synthetic? What about for my tranny?

Correct me if im wrong, GL-4 is 75w-90, GL-5 is 80w-90, Royal Purple is great and your tranny likes it too :)

GL-4 and GL-5 are grades of oil 80w-90, 90w are weights/viscositys.

I used 80w-90 GL-5 in my R154 manual trans. That is what the TSRM calls for.

I also used 80w-90 GL-5 in my LSD. TSRM calls for straight 90w GL-5, but lots of luck to you finding that at your local parts store. I know for a fact Redline sells straight 90w fluid but I was too lazy to order it and wait.

Do NOT forget to use LSD additive in your differential. You can get that at any parts store. It comes in little 10oz tubes. Drain the diff, squirt the LSD additive in first, then fill it up with oil.

Royal purple is an excellant choice for oil.

I've been using Amsoil racing gear oil in mine for about 4 yrs with no problems. I go ahead and change it every 30k miles, even though they claim 100k miles intervals.

Your only talking about 1 1/2 qts, so it not much $$.