In the conventional rear-wheel drive layout, the transmission system normally contained two sections, the "gearbox" or "transmission" mounted behind the engine, and the "final drive" mounted in the rear axle at the rear of the car. The reason for this separation of duties between the front and back of the car was to allow the drive shaft to run at lower torque, by using higher RPM. As power is the product of RPM and torque, running the shaft at higher RPM allowed more power to be transferred at lower torque. Doing so reduced the torque the driveshaft had to carry, and thus the strength and weight it required.