A differential is a type of gearbox that allows each of the driving wheels of a car to rotate at different speeds, while each wheel receives equal torque.

A car's wheels will rotate at different speeds, especially when turning corners. A differential is designed to drive a pair of wheels with equal force, while allowing them to rotate at different speeds. In vehicles without a differential, both driving wheels rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism. When cornering, the inner wheel travels a shorter distance than the outer wheel, resulting in the inner wheel spinning and/or the outer wheel dragging. This results in difficult and unpredictable handling, damage to tires and roads, and strain on the entire drive train.