How to Tell if a CV Joint Is Bad

a typical constant velocity joint or CV joint
This CV joint is clean and ready for new grease and a new boot.

Nutzdatenbegleiter / Wikimedia Commons

The CV joint is made up of hardened steel and bathed in heavy lubricating grease. The drive shaft is connected to an inner race. Most CV joints feature six hardened steel balls, which ride in grooves in the inner race. A cage keeps the balls aligned in a circle on one plane.

The CV joint housing has a set of internal grooves, which slide over the balls. The CV joints at the front wheels feature a spherical housing, which allows for up to 45 degrees turning, while those at the differentials and rear wheels are planar, allowing for only a small angular variation and a few millimeters extension or retraction. A flexible and durable rubber CV boot, sealed to the input shaft and outer housing, holds heavy grease in the joint, keeping water and other contaminants out.

This simple animation shows how the CV joint can transmit torque through such an extreme angle. Pwld / Wikimedia Commons

While the design of the CV joint makes it ideal for its placement in the driveline, there’s a lot of friction at play. Fortunately, hardened materials and application-specific lubricants keep wear to a minimum. Still, as with most things mechanical, CV joints will eventually wear out due to mileage, deterioration, or abuse. Here’s how to tell if your CV joint is going bad.

Grease Leakage

Grease leakage is one of the most common problems affecting CV joints. The rubber CV boot is constantly flexing, especially in turns, which can cause it to wear out. Exposure to the elements, even oxygen in the air, will eventually cause the rubber to turn brittle, increasing the risk of breakage. CV boots can also be damaged by road debris. In any case, CV joint grease may “spin out” of the joint, coating everything on that plane, such as the tire, brake caliper, or shock absorber.

cv joint boot showing cracking
This CV joint boot is showing some deterioration, but not leaking yet. Replacing the CV boot should keep this joint in service for a long time. Ildar Sagdejev / Wikimedia Commons

Fortunately, if you catch a leaking CV boot on time, before water and debris have contaminated the joint, you may be able to simply rebuild the CV joint. CV boot kits are relatively inexpensive. With the right tools, cleaning a CV joint and replacing the CV boot and grease can be accomplished in just a few hours.

Clicking Sounds

Clicking sounds are a clear sign of a worn CV joint. If the grease leaks out, water and debris can contaminate the joint, accelerating wear and creating excessive clearance. This clearance problem is usually noticeable in turns on acceleration, such as pulling out of a driveway or turning after a stop sign or traffic light.

You might still be able to drive with a clicking CV joint, but it's best to replace it as soon as possible. Unfortunately, once the damage to a CV joint is done, there’s no fixing it – it must be replaced. For some vehicles, new or rebuilt CV joints may be available. If available, you can save money by simply replacing the CV joint, which might take a couple hours. On the other hand, a new or remanufactured axle, which is more expensive but quicker to install, might be the only option.

Binding and Vibration

Binding and vibration are a couple of less-obvious symptoms of bad CV joints. If you notice your vehicle bucking during turns or vibrating at certain speeds, have a trusted mechanic check it out for you. Problems of this type are usually related to the axle itself, as opposed to the joint, but it's worth checking out if all other options have been explored.

mechanics inspecting under car
U-joints and CV joints can wear out, but your local trusted mechanic can help you get back on the road. Monty Rakusen / Getty Images

If you need to replace a CV joint, CV boot, or CV axle, a basic mechanic tool set will get you through most of the job, with a few key exceptions. You’ll need a 1/2-inch drive breaker bar and torque wrench and appropriate axle nut socket, usually between 27 mm and 39 mm, some of them requiring 12-point contact. The breaker bar is for removing the nut, while installing the nut will require specific torque to prevent damage to the wheel bearing – check the repair manual for the proper specification. Use a heavy brass punch for removing the inner CV joint race from the shaft or for popping the CV axle from the differential. Special tools may also be required to remove ball joints or clamp the new CV boot.