Gearbox

A gearbox, or transmission, is a mechanical device that uses a set of two or more gears working together to change the speed, torque, or direction of rotation passed from an engine to the rest of a machine. It may run at a single fixed gear ratio or offer variable ratios, whether a set of discrete gears a driver or operator selects or a continuously variable arrangement, letting an engine keep running near its most efficient speed while the output speed changes. Louis Renault, founder of the car maker that bears his name, is generally credited as the inventor of the automobile transmission, though Carl Benz anticipated the idea in 1886 by fitting his Patent-Motorwagen Nr. 2, recognized as the first practical automobile, with sprockets and chains to an auxiliary shaft and a clutch that provided a second, lower gear.