See also: Differential
Differentials are used on all modern cars and trucks, including AWD and 4WD vehicles. Differentials serve the purpose of enabling the wheels of a vehicle to spin at speeds conducive to turning and changing directions. This usually requires that the wheels on the outside of a turn must spin at a faster speed and travel a further distance to keep up with the inner wheels and to accomplish the turn successfully. The differential is a device consisting of grinding meshes that enable this. It also provides torque or power from the engine to the wheels.
Similar to open differential, the locking differential provides each wheel with the same amount of torque but does so with an electric, pneumatic, or hydraulic mechanism to lock the differentials. When indicated by a switch, the differentials will lock and the wheels will move the same speed. Locking differential is usually used on off-road vehicles, like heavy construction equipment.