The technical name for a vehicle rear end is the rear differential. A differential requires a high-tech lubricant to manage heat and wear. Some differentials are positive traction, meaning both wheels drive the vehicle. There are two major types of differentials, full-time positive traction and limited-slip positive traction. The limited slip type only locks positive when a wheel slips or spins. There is a variety of aftermarket lubricants to replace the original gear lube, including conventional oil and synthetic lubes. Synthetic lubricants are more expensive but last much longer.
Insert blocks on the front side of the front tires.
Position a floor jack under the rear differential and raise the vehicle.
Readjust the blocks in front of the front wheels, and block the backside of the front wheels, ensuring the vehicle cannot move.
Place the jack stands under each axle tube, close to the wheels, and let the vehicle down, safely, onto the stands. Remove the jack.
Return to the front of the the vehicle, and place the jack under the front, center frame section, and raise the front end.
Set two jack stands under the front frame, one under each side, near the wheels.
Unscrew the drain plug in the rear differential, but don't completely remove it. This may require inserting a half-inch breaker bar into the plug.
Place an oil drain pan under the rear differential, and remove the drain plug. Let all the oil drain.
Reinstall the drain plug, and tighten.
Replace the bottom drain plug or rear cover, whichever method was used to drain the oil.
Remove the level plug that is near the center of the rear differential. Refill the gear lube through this hole. Fill it, until oil runs out of the hole.
Thread the level plug back into the differential, and tighten it.
