A differential directs the torque of an engine to spin the wheels of a vehicle. The wheels of a vehicle spin at different speeds, especially when turning. Each wheel travels a different distance through the turn, and the inside wheels travel a shorter distance than the outside wheels. So the inside wheels have to travel slower than the outside during a turn. The front and rear wheels have different distances to travel in the same time. This also applies to the wheels in the direction of the turn as opposed to the wheels on the far side.

The intention of most differentials is to:

• Multiply the available torque (Gear reduction)
• Apply engine power to rear/front wheels
• Allow the wheels to turn at different speeds when cornering