The role of differential is to change the direction of power transmission, du, through the axle to the wheels on both sides of the transmission of power, when the vehicle turns automatically realize the two sides of the axle at different speeds, so that the wheel in the form of rolling as far as possible to do unequal distance movement, reduce the resistance when turning and reduce tire wear.

The planetary teeth in the differential only revolve around the axle gear, at this time the speed of both sides of the wheel is equal to the differential does not work, the vehicle is in a straight line.

When turning in the inside corner of the wheel received resistance, the resistance by reflecting on the axle shaft gear axle shaft, forced planetary gear rotates, begin to produce the corner inside half shaft gear speed slows down and the lateral acceleration, the is the inside of the wheel speed is slow and the lateral wheel rotation speed is accelerated, the wheels on both sides automatically into isometric exercise.