A CV shaft's purpose sounds simple: to transmit power to the wheels during constant rotation while allowing the wheel to turn.
However, it's not as simple as it seems. The component on a CV shaft that allows fluid movement with extremely little friction is a Constant Velocity (CV) joint.
This joint contains bearings inside a race and contained inside a housing on the axle shaft. When assembled, the bearings in the race act like a ball, rolling freely inside the joint a full 360 degrees.
A clip holds the CV joint and housing onto the axle shaft.
The complete joint is packed in high-temperature grease and enclosed in a rubber or polyurethane boot which is clamped to the axle shaft and the housing.
A vehicle with independent suspension will have a CV joint on both the inner and outer side of the CV shaft.
The joint must remain lubricated, clean and free of moisture. Once dirt or water enter the boot, the CV joint can quickly become damaged.
Should the concern be left uncorrected, the CV shaft may bind in the joint or housing and break, or the CV joint could disintegrate.
Once symptoms become noticeable, CV shaft replacement should be performed straight away.
Binding or hopping feeling when turning
Clicking or ratcheting noise when driving or turning
Your vehicle won't move any longer
The CV shaft is broken and hanging underneath your car.
It's a critical repair. The responsibility for transmitting power to the wheels rests on the CV shaft and its parts. If the CV shaft is damaged or broken, your car may not operate reliably.
Worse yet, if your CV shaft comes apart while you're driving your car, it could bind suddenly, cause loss of control, or cause an accident and place passengers in harms way.