An all-wheel drive vehicle uses a transmission that distributes power to both the front and rear axle separately through the use of transfer cases. Using multiple transfer cases, an all-wheel drive vehicle can redirect power to each of the four wheels independently.
The ability to transfer power to the wheels separately makes an all-wheel drive vehicle better for smooth roads, providing more traction during slippery road conditions or while making turns, as sensors inside the car detect when tires start to lose grip. Computers then adjust the power given to those wheels that still have traction. A four-wheel drive vehicle works on a similar concept, but power is evenly distributed to all four wheels at once.