Transmission is a device that transmits power from the engine of a vehicle to other parts, from which it is eventually delivered to the wheels. The transmission is a major part of a system called the drive train, a series of devices that sends engine power to the wheels.
The drive power of a car is a combination of rotational speed and torque (twisting effort). The transmission sets an engine speed that provides the wheel speed and other performance characteristics desired by the driver. The transmission can also reverse torque so the car can move backward. In addition, when the transmission is set in neutral, it delivers no power--even when the engine is running.
