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What is a CV Joint?

Katharine Swan
Katharine Swan

A CV joint, or constant velocity joint, is part of a drive shaft, the shaft that attaches to a car's transmission at one end and the wheel at the other. These joints are designed to be able to bend in any direction while continuing to turn the drive wheels at a constant velocity. They are primarily used in the drive shafts of front wheel drive cars.

Due to bumps and uneven surfaces in the road, a car's wheels tend to move up and down continuously while driving down the road; as a result, drive shafts cannot be made up of a solid shaft. The CV joint's precursor, the universal joint, was used in the drive shafts of rear wheel drive cars because of its ability to bend in any direction. With the advent of front wheel drive cars, however, car manufacturers had a new problem: the joints in the drive shafts needed to account not only for the up-and-down motions of the wheels, but also for the back-and-forth motions of steering. The CV joint is used in front wheel drive cars because of its ability to maintain a constant drive force to the wheels despite the many different kinds of movements in the front end of the car. It is often used in rear wheel drive and four-wheel drive cars, as well.

A person repairing a CV joint on a car.
A person repairing a CV joint on a car.

CV joints should be inspected periodically and may require replacement as a car ages. Each one is covered with a bulbous rubber boot that tends to deteriorate over time. When a CV boot cracks or tears open, the CV joint is left exposed to the elements, which will quickly damage the joint. If the CV axles are inspected periodically, torn boots can be replaced as needed, potentially extending the life of the joints; however, if torn boots are left unattended, the joint or the entire axle may soon need to be replaced.

Discussion Comments


90 percent of damage to a CV joint is due to the grease getting dried, whether the rubber boot is ripped or not. Consequently, inspect the grease periodically.


If you notice a CV boot ripped, or perished just get it replaced when you can. Crack and remove large nut on cv joint end in middle of the wheel/tire. Remove nut from bottom ball joint and split and pull apart. Hold down balljoint and remove it from locating hole. CV joint should pull out.

Hard part is getting cv joint off shaft by opening the circlip and pulling. Once done fit new cv boot and reinstall everything. Fill cv joint and boot with grease supplied and tie wrap both ends. Don't use the glueable CV boot rubbers!


if only one side needs replacing, is it OK to do just the one or do you have to do both at the same time?


@FastPaced- If you are able to catch a cracked or damaged boot early on, you may be able to replace the CV joint and repack it with grease before any problems occur.


The CV joint is packed with grease and protected by a rubber or plastic boot. Most problems with CV joints occur because the boot itself becomes damaged. If the protective boot becomes damaged, the grease leaks out and moisture and dirt get in. This causes the CV joint to fail as the result of corrosion and not enough lubrication.


The cost of repairing a cv joint will depend on the vehicle's make and model. In addition, certain auto stores and garages charge more for parts than others. It's a good idea to check multiple locations when purchasing/fixing a cv joint to compare prices.


Is it possible for a CV joint to be damaged from a rear-end collision (moderate to high impact)?

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    • A person repairing a CV joint on a car.
      By: Tyler Olson
      A person repairing a CV joint on a car.