REAR AXLE FLUID VISCOSITY

There are two types of rear axle available. 8.8-9.75 inch axle, use SAE 75W-140 5.50 pints (2.6 liters) 10.25 inch axle, SAE 75W-90 use 6.5 pints (3.1 liters). It is very important to check the tag located on the differential to determine if the rear end gear is a Positraction (Limited Slip Differential) or not. There is not need to check or replace the fluid unless there is a leak or has been submerged in water. The refill capacity is determined by filling the axle to 1/4 - 9/16 inch (6-14 millimeters) below the bottom of the filler hole.

Rear axle sae75w140 Motorcraft High Performance Synthetic Rear Axle Lubricant. They are called Differentials. Hope this helps. Good luck. The front differential takes 75w90 High Performance Synthetic Lubricant.