See Figure 1
A hypoid gear oil with an API classification of GL-5 or higher is required.
If the average ambient temperature is above -10°F (23°C), use SAE 85W-90.
If the average ambient temperature is -10°F to -30°F (-23°C to -34°C), use SAE 80W-90.
If the average ambient temperature is below -30°F (-34°C), use SAE 75W.
Rear axle lubricant level is checked at the filler plug in the rear of the differential housing. Use the proper size open end wrench (usually 15 / 16 in.) to remove the filler plug. Insert your finger into the hole; the gear oil level should be right at the plug opening. Use an SAE 80 or 90 gear oil to bring up the differential oil level.
DRAIN AND REFILL
Place a drain pan under the rear axle housing and remove the lower drain plug. When the fluid has stopped draining, clean the threads on the drain plug and screw it into the housing. Tighten the drain plug and fill the housing to the proper level through the filler plug hole.