A drive axle is an axle in a vehicle which is powered by an engine. People most commonly think of cars when they think about drive axles, with some cars having the front axle driven by the engine, while others have their rear axles driven by the engine. In all wheel drive cars, the engine supplies power to both axles and all four wheels. This axle is a critical part of the systems which allow a vehicle to move down the road.
The drive axle is also a fairly complex piece of equipment. First, energy must be transferred vertically from the engine, and the drive axle must respond to input from the steering wheel as well. The car is also geared to use energy as efficiently as possible. As a result, several interconnecting systems interface with the drive axle to power it, control its movement, and increase efficiency.
While people may think of an axle as a solid object, the drive axle is actually split. This is because both of the driving wheels do not necessarily turn at the same speed at all times, making it necessary to add some equipment which will allow for movement at different speeds. Whenever someone turns a corner with a car, for example, the inside wheel slows down, because it has less ground to cover, while the outside wheel speeds up, allowing the car to corner smoothly.