Transmission

A series of gears and shafts used to provide multiple gear ratios necessary for efficient engine operation at varying vehicle speeds. Usually contains between 3 and 6 separate speeds.

Transfer case

An additional series of gears used to provide a power split between front and rear axles of a four wheel drive vehicle. They often contain additional gearing to allow for more control during slow off road maneuvers.

Driveshaft

A long hollow piece of metal used to transfer rotational force from one gearing unit to another.

Universal joint

A joint used in driveshafts to allow the shaft to transmit power at angles. (often used in conjunction with a slip joint to allow length changes too)

Constant velocity joint

Similar to a universal joint but more compact and better able to handle extreme angles of operation

Differential

A device that transfers power from one driveshaft to two axle shafts. The differential also compensates for the different wheel speeds on the axle as the vehicle turns or encounters uneven terrain.

Axle shafts

Shafts usually contained within an axle that transmit power from the differential to the wheels.