The Bus

I'm replacing the diff on my C4 track/race car [NASA ST2]with a rebuilt unit. Which Redline diff oil do I need to use??? Weight??? I know to fill the diff till it runs out the fill hole but about how many quarts is that?? I already have purchased the GM limited slip additive. I bought two bottles ; do I need them both????

Thanks for all information.

Aardwolf

I used the 75w90 heavy shock proof and did not add more additive as it comes added already. Did your rebuilt parts come with any recomendations? Also consider schaeffer's.

http://www.schaefferoil.com/gear_oils.html

http://www.bobistheoilguy.com/gearoiltest.htm

FasterIsBetter

Red Line 75W90. It is a hypoid modified gear oil. Do NOT add any of the GM limited slip modifier. The 75W90 already has all the modifiers you need in it.

(Do not use Red Line 75W90 NS. That is only for transmissions, not differentials, does not have the limited slip modifiers in it).

IIRC, the diff takes about 3 1/2 to 4 qts.

lbarnard

I use Red Line High Temp gear oil and I do add the GM additive. I have had no issues.