Components of the driveline are designed to smoothly transmit the rotating power of the engine, while still allowing suspension to flex and wheels to alter direction. Front wheels are usually driven by an axle that includes constant velocity, or CV joints. Differentials allow for the turning rate of a pair of wheels to be different, which is necessary during cornering.
Four wheel drive vehicles have two differentials, one for the front wheels and another for the rear wheels. A transfer case is a switchable gearbox that delivers power to the front and rear differentials. The transfer case is connected to the differential by the driveline.
All wheel drive vehicles use a similar concept, however the transfer case is replaced with a centre differential, which usually allows more or less engine power to be delivered to each axle.
Components of the driveline distribute power to each wheel as required.
The differential allows each wheel to act independent from the others.