Can someone tell me what weight rearend-fuild I should use in my 88IROC with a 7.5 10bolt. Car has 3.73 gears that were put in 8 years ago.

What is the stock weight fluid and should I upgrade the weight at all?

Thanks,

 

Stock is about 80W-90.

Typical replacements are about the same; 75W-90 is more common nowadays.

Any of the name brand fluids is fine. Synthetic is best (Mobil 1, Amsoil, Royal Purple, Red Line), NOT the "me-too" ones. Also, stay way from the super heavy kinds, like the 85W-140 or Lakewood BFL. It's too thick for these rears in normal street duty.

Don't forget to use the posi additive, if you have posi; it's also called friction modifier. Put that in, then fill it the rest of the way with the lube. I'd suggest the GM stuff as opposed to parts store variety.

 

True that, GM stuff is great, 80-90 weight AKA gear oil is basically all you need.

 

I prefer synthetic (Mobil 1 75W-90), though 82 is correct.

JamesC

 

Dont want to be a highjacker ,but what is mineral bace oil is it just nonsynthetic.