Learn About Constant Velocity Joints

How does a constant velocity joint work?

Constant velocity, or CV, joints are used to connect your vehicle’s transmission to your wheels. CV joints are part of the driveshaft and are used primarily on front-wheel drive vehicles, but they are also used in rear- and four-wheel drive vehicles. Each drive wheel has two CV joints: the inner joint connects the transmission to the axle, and the outer joint connects the axle to the wheel. The CV joint’s name comes from its ability to move with your vehicle’s suspension in any direction (if your vehicle hits a pothole or an uneven surface) and still be able to keep the drive wheels moving at a constant velocity. The CV joint is a very special joint: it connects two different rotating shafts. These two rotating shafts are stuck in a fixed position; so, the CV joint must be able to move and bend to keep these two shafts connected. CV joints are being used in newer vehicles and are taking the place of the old “U” joints. The CV joint is able to transmit even levels of torque to the wheels continually no matter what angle it’s in. This means that no matter how many potholes you hit, or if the vehicle is turning, the CV joint will keep the drive wheels moving at a constant velocity.

Why do you need to replace a constant velocity joint?

CV joints are required to keep your drive wheels moving at the same speed. The joints are needed to provide the connection between your suspension and your wheels. If you think about it, when you are driving, even down a straight road, your wheels are constantly bouncing up and down over the road. CV joints are the only part of an otherwise solid driveshaft that bends with the road, and while the vehicle is turning. Again, without properly working CV joints, your wheels would be moving at different speeds when you are steering or hit an uneven surface.

When do you need to replace a constant velocity joint?
CV joints last from 70,000 to 130,000 miles, and over, but technicians recommend that they be inspected periodically. Your CV joint is composed of six steel balls that roll along grooves in a rotating ball-and-socket joint plus a steel cage, which holds the balls in place and moves as the balls roll along the grooves. So, as you can see, there are many moving parts in a CV joint. This is why a rubber boot is required to cover the joint and keep the joint’s grease clean. Over time, these boots can wear and crack. If the boot does crack, the CV joint will be exposed to wet roads and other debris. The joint will also lose its lubricating grease, which will further damage the joint’s moving parts. CV joint boots are visible under your vehicle and are easy to inspect. If they look worn or torn in any way have them replaced, and this can extend the life of your CV joint. You can also watch for any noises or vibrations coming from your front suspension or a loss of acceleration when you are turning. If you experience either of these two things, you may have a problem with your CV joint, and you should have it inspected and replaced if necessary.

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