Hi,

I was thinking about going with the Redline synthetic gear oil 75W90 with the friction modifier. However, I have heard/read people suggest to use the regular 80W90 gear oil instead in a 8 3/4 with sure grip.

I think both the Redline (depends which one) and Lucas differential oils contain the limited slip additive already. So I guess this is more of a synthetic vs conventional question than anything else.

The car is a 1968 Barracuda with a sure-grip unit, 3.91's, street driven, not drag raced. Differential was taken apart to inspect and now going back together. Everything looks really good (bearings, gears) so no new bearings or gears. They both have about 15-20k tops on them.

What have you used and/or currently using that has worked for you? What would you recommend for my application?

Thank you in advance