IPA: /ˈɡɪərbɒks/
KK: /ˈɡɪrˌbɑks/
A protective case that holds a set of gears, which helps to transfer power from the engine to the wheels in a vehicle.
The mechanic checked the gearbox to ensure it was functioning properly.
**Gearbox** → The word is formed from "gear" (from Old English *gier*, meaning a mechanism for transmitting power) and "box" (from Old English *box*, meaning a container). A gearbox is a container that houses gears for transmitting power in machinery.
Think of a 'container' ('box') that holds 'mechanisms for power' ('gear') — that's what a gearbox does.
No commonly confused words.