gearbox

US /ˈɡɪr.bɑːks/
UK /ˈɡɪr.bɑːks/
"gearbox" picture
1.

a set of gears with their casings, especially in a motor vehicle; a transmission.

:
The mechanic replaced the faulty gearbox in the car.
A smooth-shifting gearbox is essential for a comfortable drive.