Self alignment couplings - Constant velocity (CV) joint

Constant-velocity joints (also known as homokinetic or CV joints) allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play. They are mainly used in front wheel drive vehicles. Modern rear wheel drive cars with independent rear suspension typically use CV joints at the ends of the rear axle halfshafts and increasingly use them on the drive shaft.

Constant-velocity joints are protected by a rubber boot, a "CV gaiter", usually filled with molybdenum disulfide grease. The six spheres are bounded by an anti-fall gate that prevents the spheres from falling when the shaftings are perfectly aligned. Cracks and splits in the boot will allow contaminants in, which would cause the joint to wear quickly as grease leaks out. (Parts in contact would not get proper lubrication, small particulates would cause damage and scratching, while water ingress causes metal components to rust and corrode.) Wear of the boot often takes the form of small cracks, which appear closer to the wheel, because the wheel produces most of the vibration and up and down motions. Cracks and tears in the areas closer to the axle are usually caused by external factors, such as packed snow, stones or uneven rocky off-road paths. Aging and chemical damage can also cause boot failure.

Signs that a CV joint is failing:

CLICKING" NOISES WHEN TURNING
Though it's sometimes described as a loud click and sometimes described as a pop, this noise is unmistakable once you hear it. It presents itself when you turn the vehicle, and it's due to the loose joints of a worn CV axle. As with other symptoms, it's important to bring your vehicle to a service centre immediately if you hear this noise.

 A KNOCKING SOUND
Keep an ear out for a knocking or clunking sound, especially a rhythmic one. While this doesn't always come from the CV axle, none of the potential causes are good ones, so an immediate inspection is required. In some cases, you may notice that the knocking sound is more pronounced in reverse. Ultimately, your best bet is to have the experts inspect the problem right away. If you're not sure how safe the vehicle is to drive, give us a call. We'll discuss the issue with you and help make arrangements if necessary.

GREASE ON THE INSIDE OR EDGE OF THE TIRES
The CV axle joint has boots that contain grease while the axle spins, keeping it from leaking. If the boot develops a leak, the resulting lack of lubrication could soon lead to the failure of the CV joint. If you notice grease on the edge of your tire or the inside of the wheel, don't wait to bring your car in for service.

VIBRATION WHILE DRIVING
This is a tricky one, since there are many things that could cause vibration when you drive. However, if the vibrations are excessive, increase with speed, or give an unusually "bouncy" feel to your drive, it may be due to the CV axle. Whatever the cause of vibrations, it's important to get your vehicle inspected; if it vibrates too much, it can become harder to control.
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