Gearbox
A metal casing containing a system of gears that alters speed and torque ratios, often synonymous with the transmission.
A gearbox is a structural metal casing that houses a system of gears, shafts, and bearings designed to alter the speed and torque ratios between an engine and the drive wheels. In automotive contexts, "gearbox" is often used synonymously with manual transmission, but it can also refer to transfer cases, differentials, and steering gears.
The gearbox contains gears of different sizes that are engaged to match the vehicle's speed and engine RPM. It relies on gear oil or transmission fluid to lubricate the moving teeth, cool the components, and damp mechanical noise. The casing features seals around the input and output shafts to keep the fluid contained.
Symptoms of gearbox wear include whining or growling noises (indicating worn bearings or worn gear teeth), difficulty shifting, gear slipping, and fluid leaks from the shaft seals or casing joints. Regular fluid changes are necessary to remove metal wear particles and maintain proper lubrication.