differential question

[pitman]

I have a 64 Cutlass.The differential cover gasket is being replaced.Can I refill the rear with 85-140 gear oil ?? or should I stick with the 90 wt. that I think is currently in it??

[NTX5467]

Unless the factory recommendations allow for the 85W-140 oil, I'd stay with the "normal" 90-weight viscosity oil. The heavier viscosity oil is "stiffer" and will result in additional power consumption than the 85W-90 which was common when the car was new.

Just some thoughts,

NTX5467

[pitman]

tHANK-YOU---I will stay with the 90 wt.

Pitman

[Guest Jim_Edwards]

Unless the factory recommendations allow for the 85W-140 oil, I'd stay with the "normal" 90-weight viscosity oil. The heavier viscosity oil is "stiffer" and will result in additional power consumption than the 85W-90 which was common when the car was new.

Just some thoughts,

NTX5467

Not only that but in a cold climate the drag from the thicker oil might become great enough to make it seem you were pulling 5,000 lbs of dead weight. I knew an idiot once that filled the differential on his Jeep with STP. Needless to say the first near Zero day it was impossible to get the Jeep to move. Might have been impossible to push that Jeep even in neutral with anything short of a bulldozer.

[junkyardjeff]

The guy who rebuilds my differentials told me the 85W-90 is much thinner then the 90 weight of years ago and recommended 85W-145.