The final drive is another gearset which delivers transmission output to the drive axles, and includes the differential. When a car turns, the wheels on the outside of the turn have to turn slightly faster than those on the inside, since they have to travel a larger arc in an equal amount of time. The drivetrain must be able to transmit power to the wheels and still allow for these variations in wheel speed when cornering. The device which allows this, called the differential, uses a system of gears to allow a speed differential between wheels on opposite sides of the car.