1) Auto part 2) Auto transmission 3) BMW transmission 4) Case 5) Casing 6) Gear case 7) Shell 
Contains the gears & piston.
A casing for gear sets that transmit power from one rotating shaft to another. A gear box has a number of functions: it is precisely bored to control gear and shaft alignment, it contains the gear oil, and it protects the gears and lubricant from water, dust, and other environmental contaminants. Gear boxes are used in a wide range of industrial, a...
a series of shafts and gears which varies ratio of engine to rear wheel speed. Motorcycle gearboxes use from two to seven speeds or ratios.
Gearbox is British slang for the female genitals.
[n] - the shell (metal casing) in which a train of gears is sealed
gear case noun the shell (metal casing) in which a train of gears is sealed
A metallic enclosure containing several cogs, each one affecting the effort in which the car moves. Each cog/gear has a different mph ratio per 1000rpm. Overall control maybe manual via the gear stick, automatic, or semi via a hand paddle.