The differential transfers torque from the drive shaft or transmission output to the differential’s drive axles.  The transfer case attaches to the transmission and connects to both the front and rear drives axles of a four-wheel-drive vehicle.

The fluid that lubricates the differential & transfer case provides lubrication to gears, bearings, shafts, and other internal components.  Heat, pressure and friction slowly breakdown the additives in the transfer case fluid. In addition, small particles of metal may come off the gears as they wear and these metal particles can mix with the fluid. Fluids can also become contaminated with water. Eventually, the protective additives in gear oil break down.

Replacing the differential & transfer case fluid at the manufacturer’s required service interval will help to prolong the life of the gears and bearings.