Transmission system in a car helps to transmit mechanical power from the car engine to give kinetic energy to the wheels. It is an interconnected system of gears, shafts, and other electrical gadgets that form a bridge to transfer power and energy from the engine to the wheels. The complete setup of the system helps to maintain the cruising speed of the car without any disturbance to the car’s performance. The oldest variant of the transmission system in India is the manual transmission that has undergone various modifications and alterations to form the present day automatic transmission.

A transmission or gearbox provides speed and torque conversions from a rotating power source to another device using gear ratios.  The transmission reduces the higher engine speed to the slower wheel speed, increasing torque in the process.  A transmission will have multiple gear ratios (or simply “gears”), with the ability to switch between them as speed varies. This switching may be done manually (by the operator), or automatically.  Directional (forward and reverse) control may also be provided.

In motor vehicle applications, the transmission will generally be connected to the crankshaft of the engine. The output of the transmission is transmitted via drive shaft to one or more differentials, which in turn drive the wheels.

Most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft (e.g. a motor crankshaft). This means that the output shaft of a gearbox will rotate at slower rate than the input shaft, and this reduction in speed will produce a mechanical advantage, causing an increase in torque.