Axle lubricant lives a hard life, sheared between hypoid gear teeth under high contact pressure and heat. A synthetic 75W-90 holds its film strength better than a conventional oil under that load, which is why it is the factory specification here. The MS-8985 standard is what tells you the additive package matches what the differential was designed around.

Fluid Specifications:

• SAE 75W-90 synthetic axle lubricant.
• Meets Chrysler Material Standard MS-8985.
• For select Chrysler, Dodge, Jeep and Ram axle applications.
• 32 oz. bottle.
• Check whether your axle requires a limited slip additive before filling.