Posi Diff Gear Oil ?????

[big gear head]

Which differential was used in the rebuild? Was it a Eaton Posi, Auburn, traction Lock or something else? Some differentials need more additive than others. The Eaton Posi and traction Lock usually only need one bottle of the GM additive. The Auburn usually needs two bottles.

I don't use 140 oil in a car. The 80W90 or 75W90 is plenty for a car. If you are towing with a truck then the 140 would be fine. If you can find Torco TGO or TRO oil then use it. I've been using Lucas in a lot of rear ends lately, and Mobile 1 if I want a synthetic.