What is the diffrence between 80/90 weight gear oil and 75/140 weight synthetic gear oil?

There is different additives and detergents added to these specific gear oils, as well as the diffence is viscosity. You should stay with what your manaufacturer requires, but you can get 80/90 in synthetic.(Castrol Syntorc) When changing your rear diff fluid, some vehicles require a limited slip additive, so be sure to check your owners manual.What is the diffrence between 80/90 weight gear oil and 75/140 weight synthetic gear oil?
The viscosity. You should stick with the specific specific weight oil that your vehicle takes. Using synthetic oil is better than regular gear oil, as it usually lasts about 80K miles with normal use.What is the diffrence between 80/90 weight gear oil and 75/140 weight synthetic gear oil?
YH! What they said.
viscosity