I use Amsoil Severe Gear 75w-90 synthetic in my race car, tow truck and everyday truck. They also have 75w-110 and 75w-140. The lighter viscosity will free up a bit more power and mpg if you don't need the higher viscosity versions.It all has a limited slip additive but on rare occasions, you may have to buy some seperately.

Amsoil Severe Gear 75w-90

Good stuff which my differential guy like also.