How to Tell if You Have a Bad CV Axle or Half Shaft

Alex Palmeri
April 13, 2018


Symptoms of a bad CV axle shaft

Clicking sound when turning: The most common symptom of a bad CV axle is a clicking noise when turning. This is most often heard during sharp turns at lower speeds. Typically this indicates an issue with the outer CV joint, and the sound is the loudest on the joint that’s opposite of the turning direction.

Clunking sound on acceleration or deceleration: When the inner CV joint begins to fail, you may experience a clunking sound when accelerating or quickly letting off the throttle to prepare for braking. This can also be an issue with your transaxle, differential or U-joints but it’s important to inspect the CV joints if a clunking is present.

Grease on the inside of your tire: Because both joints are protected with a rubber boot that contains grease, any tear or crack in the boot can result in grease leaking out. When this happens, it’s common to see grease on the inside of the tire, steering and suspension components, and on the ground. The boot can be replaced in most cases, and this does not automatically warrant replacement of the entire CV axle.

Vibration while driving: If the shaft of your CV axle is bent, you may begin to experience a vibration while driving. This will become more pronounced as you increase speed. It’s best to have the area surrounding the CV axle inspected for physical damage. 

» MORE: Get an estimate for your CV axle replacement 

CV axle repair advice

Your CV axles are not a maintenance item, but they do require inspection at specific intervals. Check your owner’s manual for time and mileage intervals, or have the axles inspected at least once a year.

If you begin to experience any of the above symptoms, contact your mechanic immediately. These axles are extremely important — they’re the final link between your transaxle or differential and your wheels. A broken CV axle presents a safety concern, as the axle can damage surrounding parts as it spins freely. This would leave your car inoperable and would require a tow.

Your auto repair shop will inspect the CV axles for physical damage, excessive play and the condition of the protective rubber boots. In some cases, just the boot can be replaced, and the CV joint can be lubricated with new grease. If there is excessive play in either joint, it’s typically more cost effective to replace the entire CV axle rather than attempting a repair. There is no need to replace CV axles in pairs as long as the other axles are in good condition.

There are many aftermarket CV axles on the market, but it’s much smarter and safer to use either the factory part from the manufacturer or a replacement of equal quality. 

The cost to have your CV axle replaced or repaired can vary drastically. The major factors here are the cost of parts, labor time and how many CV axles need to be replaced.

Only someone who has considerable experience in replacing suspension components and access to vehicle-specific repair information should try this repair on their own. The possibility of damaging the transmission or other suspension parts means this job is best left to a professional mechanic.

Get it diagnosed by a professional

What does a constant velocity (CV) axle do?

A constant velocity (CV) axle, also called a “half shaft,” is an important part of your vehicle’s drivetrain. It’s responsible for transferring the power from your transmission to your wheels. Because the CV axle is constantly rotating and flexing to accommodate different road conditions, it can wear out and fail.

The CV axle consists of a shaft with an inner and outer CV joint. The CV joints are protected with rubber boots and use a special grease for lubrication. The flexible CV joints allow for a smooth power transfer due to their ability to move up and down with the suspension or side to side when turning your front wheels. 

CV axles can last a long time but will eventually wear out. Thankfully, they provide many warnings signs before a complete failure.


Alex Palmeri

About the Author

Alex Palmeri worked nine years as a master technician at Mercedes-Benz of Chicago and is currently the foreman at a large fleet garage. He writes about automotive news, maintenance and racing, and runs a YouTube channel called Legit Street Cars.

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