My Mechanic Says I Need New CV Joints. What Are They and Why Do They Fail?

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Cars that drive their front wheels use constantly velocity joints. What you need to know.

What Are CV Joints?

Constantly velocity joints (CV Joints) are part of the front wheel drive or all-wheel drive assembly that many popular cars use. The joint allows a shaft to transfer power from the transmission to the wheel while the angle changes. Imagine a drive shaft that is being pushed up and down as a car goes over bumps and turns corners. On each side of a car, there are two. One inside next to the transmission, and one outside next to the hub of the wheel. Other names for the assembly include “CV Axles” or “CV Assemblies.”

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How Do I know if My CV Joints Are Going Bad?

The usual symptom of a bad outer CV Joint is a clicking noise that can be heard when turning, but not when going straight ahead. To verify that diagnosis, find some open space like a parking lot and put the car in reverse. Turn the wheel all the way to one side and slowly roll backward with the windows open. If the noise is louder and clear to hear, you need to see a mechanic. Inner CV joints may produce a hum, shudder, and vibration at speed. A (new) clunk when you put a car into Drive is also a bad sign that could indicate a bad CV joint.

Why Do CV Joints Fail?

Typically, CV Joints are built to last the life of the car, and they will in most cases. However, it is an imperfect world and road debris can sometimes pierce the rubber boots over the CV joints. The boot will then fail over time due to movement and the grease in the boot will be flung out. That situation allows dirt and water in and then the bearings fail. We spoke to master mechanic Mark McMullen at G&M Services in Millis, Mass. and he told us that despite popular belief, it isn’t routine pot holes or bad roads that kill these joints. Normally, it is a failed rubber boot.

What Can It Cost To Replace A Set of CV Joints?

The CV Joints are often replaced as a pair and a repair on a compact car can run up to about $750. Expect to pay more for premium cars and performance cars.

 

Image Notes: Top Image courtesy of BMW and GNK Driveline. Parts shown are VL3 CV Joints.

 

 

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John Goreham

John Goreham