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.
In British English
In British English, the term transmission refers to the whole drivetrain, including clutch, prop shaft (for rear-wheel drive), differential, and final drive shafts..
In American English, however, the term refers more specifically to the gearbox alone, and detailed usage differs.
Early transmissions included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, in support of pumping, milling, and hoisting.
Many typical automobile transmissions
Many typical automobile transmissions include the ability to select one of several gear ratios. In this case, most of the gear ratios (often simply called “gears”) are used to slow down the output speed of the engine and increase torque.
However, the highest gears may be “overdrive” types that increase the output speed.
Gearboxes have found use in a wide variety of different—often stationary—applications, such as wind turbines.
Transmissions are also used
in agricultural, industrial, construction, mining and automotive equipment. In addition to ordinary transmission equipped with gears.