Rear Axle Operation

A differential has two side gears and two pinion gears. Some differentials have more than two pinions. Each side gear is splined to an axle shaft, so each axle shaft must turn when its side gear rotates.

The pinion gears are mounted-on a shaft, and are free to rotate on this shaft. The pinion shaft is fitted in a bore in the differential case and is at right angles to the axle shafts.

Power is transmitted through the differential as follows the drive pinion rotates the ring gear. The ring gear, being bolted to the differential ease, rotates the case components. The differential pinion, as it rotates with the case components, forces the pinion gears against the side gears. When both wheels have equal traction, the pinion gears do not rotate on the pinion shaft because the input force on the pinion gear is equally divided between the two side gears. Therefore, the pinion gears revolve with the pinion shaft, but do not rotate around the shaft itself. The side gears, being splined to the axle shafts and in mesh with the pinion gears, rotate the axle shafts.

The differential allows the wheels to turn at different rates of speed while the axle continues to transmit the driving force. This prevents tire scuffing when the vehicle is turning and premature wear on internal axle parts.