A transmission or gearbox provides a speed-torque conversion (commonly known as "gear reduction" or "speed reduction") from a higher speed motor to a slower but more forceful output or vice-versa, using the principle of mechanical advantage.

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.

Most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft (e.g. a motor drive shaft). This means that the output shaft of a gearbox will rotate at slower rate than the input shaft. This reduction in speed will produce a mechanical advantage, causing an increase in torque. A gearbox can be setup to do the opposite and provide an increase in shaft speed with a reduction of torque. Some of the simplest gearboxes merely change the physical direction in which power is transmitted.

Many typical automobile transmissions include the ability to select one of several different gear ratios. In this case, most of the gear ratios (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, such equipment makes extensive use of the hydrostatic drive and electrical adjustable-speed drives.




Case Studies

An Investigation of 15 units Pulverizer Gear Box High Vibration Problem at Tanjung Bin Power Plant, Serkat Pontian Johor Darul Takzim, 2008

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An Investigation of Turbo Expander Gearbox Vibration Problem, 2005
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