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What is a CV Axle?

What Does a CV Axle Do?

Part of the drivetrain of most front-wheel drive (FWD) vehicles, constant velocity (CV) axles take power from the transmission and transfers it to the wheels to allow the vehicle to travel down the road, move over bumps, and turn left and right. 

CV axles get their name because they constantly maintain the velocity of the wheel and axle rotation no matter the angle of the axle or wheels. When turning or driving over a pothole or bump, constant velocity axles deliver constant power no matter what the angle of the wheels are. Additionally known as a half shaft or an axle shaft, CV axles can also be found on rear-wheel drive (RWD) and all-wheel drive (AWD) vehicles equipped with an independent suspension.

What Are the Parts of a CV Axle?

A CV axle features an inner CV joint that connects the half shaft to the transmission and an outer CV joint that connects the CV axle shaft to the front wheels. These joints allow the CV axle to move as the vehicle travels over bumps. Without CV joints, the axle would break when the vehicle makes a turn or hits a bump. In addition, the inner and outer CV joints both have a boot that is filled with grease.

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How Many CV Axles Does a Vehicle Have?

Front-wheel drive vehicles have two CV axles – one that connects each of the front wheels to the transmission while AWD vehicles have four CV axles – two that connect the front wheels to the transmission and two that attach the back wheels to the rear differential.

What Causes a CV Axle to Fail?

While CV axles typically have a long lifespan with some lasting more than 100,000 miles, they can fail for a few different reasons.

Boot Rupture

A common cause of CV axle failure is a rupture to the boot. When the boot ruptures, the CV axle loses grease and is no longer lubricated. In addition, the tear can allow water and debris to get in the boot making it susceptible to premature failure.

Wear and Tear

Normal wear and tear can cause a CV axle to go bad. Your driving habits and the environment that you drive in can affect the lifespan of CV axles.

Lifted Vehicle

Installing a lift kit on a vehicle increases the distance between the differential and wheel hub. This puts the CV axle at an extreme angle that can cause it to fail prematurely. 

Signs of a Failing CV Axle

If a CV axle is failing, it can affect how your vehicle handles. Recognizing the signs of a failing CV axle is key to ensuring that your vehicle is operating properly. If you experience any of these symptoms of a bad CV axle, have your automotive technician examine your vehicle.

Clicking Noise While Turning

A clicking or popping noise when turning can indicate an issue with the outer CV joint. It can be more prominent when making sharp turns at lower speeds.

Grease on Wheels

The CV axle’s boot is greased and if the boot becomes damage, the grease can leak onto the inside of the wheels.

Clunking Sound

A clunking sound when accelerating or decelerating can be a sign of a failing inner CV joint.

Vibration

Excessive vibration, especially at higher speeds, can be a sign of a bad CV axle. While vibration can be a sign of other issues, it is important to have your vehicle examined if you’re experiencing vibration.

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Should Both CV Axles Be Replaced at the Same Time?

Many auto technicians recommend replacing both the left and right CV axles at the same time. The rationale is that if one axle has failed, the other one is likely not far behind since both axles have been used under the same conditions. Replacing both axles at the same time can help save on future repair costs.

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The content in this article is for informational purposes only. You should consult with a certified technician or mechanic if you have questions relating to any of the topics covered herein. Tenneco will not be liable for any loss or damage caused by your reliance on any content.

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