An axle shaft is a component of a vehicle with a solid axle design that was commonly found in most vehicles of the past. Today, most passenger cars and light SUVs feature independent suspension systems, although many trucks and larger SUVs still rely on solid axles.
A solid or “rigid” axle is a metal housing that connects the wheels on each side of a vehicle, right and left. It creates something known as a “dependent” suspension, where the movement of one wheel upwards and downwards affects the other, since they are each connected to the same solid axle. A solid axle can be either a “dead” axle (one that simply connects the wheels) or a “live” axle (one that drives the wheels).
When an axle is a “live” drive axle, it is made up of a gearbox (the differential) that receives rotational torque from the drive shaft coming from the transmission. Protruding from each side of the differential are heavy metal tubes that connect to the wheels. Inside the tubes are the axle shafts (sometimes referred to as “half-shafts”) that rotate as a result of the gears in the differential to turn the wheels.
This arrangement was popular for the rear wheels of most vehicles prior to the 1980s. It was also used for the front wheels of four-wheel-drive trucks.
Chances are that your vehicle has CV axles as part of an independent suspension design. In that case, the signs of a bad CV axle can be different than those of a bad axle shaft. If, on the other hand, your vehicle features a live solid axle (as with many trucks or older vehicles), where the axle shafts inside the axle assembly rotate to provide power to your wheels, then you might notice one or more of the following symptoms if an axle shaft fails:
It is far more common to replace an axle shaft bearing or seal than the axle shaft itself. However, if your vehicle needs a new axle shaft, a technician will take the following general steps: