CV axle joints stand for “constant velocity” axle joints. These types of axle joints are used primarily in front wheel drive cars. However, they’re being seen more often lately as rear drive axles as well.The function of a CV joint is to allow a drive axle that sits on a horizontal plane to articulate to meet the hub of the drive wheel, delivering power to the front drive wheels. Steel shafts don’t bend and they certainly don’t make for a smooth ride when they are bent. The CV joint allows for an angle from the horizontal shaft to the wheel hub.
Imagine the basic components of your car. You have an engine and then your transmission. The transmission “translates” engine power into moving power. For a front wheel drive car, the transmissions are typically mounted transverse, meaning that the output shaft runs from side to side in the car instead of front to rear. If those axle shafts did not have a way to move or articulate as a wheel moves over bumps or go around turns, the axle shafts would either fall out of the hub or bind and sheer off splines or the teeth of the shaft. By having a CV joint, the driving axle shaft does not have to fit directly into a wheel hub. It has a moving joint on the end that is mated to another moving joint. By having this articulating joint, your car can move over bumps and go around corners without fear of breaking.
Newer rear wheel drive vehicles with independent rear suspension also have a similar setup. However instead of the axle shafts going from side to side out of the transmission, a drive shaft from the rear of the transmission travels the length of the car and mounts to a differential. The differential is a ring and pinion gear located in the rear axle housing. The pinion is attached to the end of the drive shaft with a u-joint (universal joint). The pinion gear sits on the ring gear, the axle shafts sit in teeth of the ring gear. As the drive shaft turns the pinion gear, the pinion turns the ring gear. As the ring gear turns it is turning the axle shafts. At the end of the axle shafts are CV joints with stub shafts that attach to the hub. A good view of the CV axle shafts can be seen in a Honda CRV utility vehicle.
Most all CV axle joints are covered with a protective boot that keeps a significant portion of dirt and grime out. To determine if you have a problem with your CV axle shafts, turn the steering wheel all the way over until it stops and drive in a circle. If you hear a definite popping noise, chances are you having a CV joint going bad.