A car differential is a mechanical device found in the drivetrain, usually between the drive wheels (either at the front, rear, or both). Its main purpose is to allow the wheels to rotate at different speeds while still receiving power from the engine. Why is this needed? When a car turns, the wheels on the outside of the turn travel a longer distance than the wheels on the inside. If both wheels were forced to spin at the same speed (like with a solid axle and no differential), the tires would