| The method of providing traction to any of the wheels of a vehicle, as conditions require. Depending on the system, it may be full-time or part-time. | |
| The top of the engine block where the cylinder head is attached | |
| Enclosure for the differential and pinion gears. Can be removable are integral part of axle housing. Also called differential housing | |
| Electric current that flows in one direction, from positive to negative then reverses direction, from negative to positive. |