The transmission box which is also known as the gear box is the second element of the power train in an automobile.A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term transmission refers simply to the gearbox that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device. uses: Gearboxes have found use in a wide variety of different—often stationary—applications, such as wind turbines.