What constant velocity joints are and why they need checking

Constant velocity joints, or CV joints, connect your axles to your wheels and let power flow to the wheels while they turn and move up and down. They're packed with grease and covered by rubber boots that keep that grease in and dirt out. When a boot tears or a joint wears out, you'll hear clicking when you turn, feel vibration at highway speed, or see grease splattered inside your wheel. Checking them takes about 20 minutes per side and requires no special tools beyond what's in a basic toolkit.

Most CV joints last 80,000 to 100,000 miles, but that depends on driving conditions, road salt, and how well the boots stay intact. A torn boot can shorten that life to a few thousand miles because water and grit get inside. Catching a torn boot early means replacing just the boot and regreasing the joint—a $150 to $300 job. Waiting until the joint itself fails means replacing the entire axle assembly, which runs $400 to $800 per side.

Key Takeaways

  • CV joint boots are rubber covers that protect the joint's grease; a tear in the boot is the first sign of trouble and the easiest to catch early.
  • You can inspect boots visually by turning the wheel fully left or right and looking at the accordion-like rubber on the inside of the wheel, checking for splits, cracks, or grease spray.
  • A clicking sound when turning at low speed, especially in tight parking lot turns, is the most common symptom of a worn CV joint itself.
  • Vibration that gets worse as you speed up usually points to a joint that's already damaged inside, not just a torn boot.
  • If you find a torn boot, have it replaced before the joint wears out; if you hear clicking or feel vibration, the joint itself likely needs replacement.

Visual inspection of the CV boots

Park on level ground and turn the steering wheel all the way to the left. Crouch down and look at the inside of the right front wheel. You're looking for the CV axle, which is a shaft running from the transmission area toward the wheel. On each end of that shaft, you'll see a rubber accordion-shaped boot. This is what you're checking.

Look for splits, cracks, or tears in that rubber. Grease splatter on the inside of the wheel or on the tire sidewall is a sign the boot has already failed. If the boot looks intact and dry, move to the other side: turn the wheel all the way right and inspect the left CV boot the same way. Repeat this check every six months or whenever you rotate your tires, because a small tear can grow quickly.

Some boots develop a bulge or ballooning, which means the internal pressure has built up—usually from a small tear that's already letting water in. A bulging boot should be treated as a failure and replaced soon, even if you don't see a visible split yet.

Testing for clicking and listening for noise

Drive to an empty parking lot and make tight left turns at 5 to 10 mph. Listen carefully for a clicking or popping sound that speeds up as you turn tighter. That sound is the outer CV joint on the right side (the outside of the turn) clicking because the balls inside are worn and have play in them. The tighter the turn, the more the joint flexes, and the louder the click.

Now make tight right turns and listen for the same sound on the left side. If you hear clicking only during turns and not while driving straight, it's almost certainly a CV joint. If the clicking happens while driving straight, it may be a different suspension component, but a worn CV joint can still be the cause.

Clicking is a sign the joint itself is worn and needs replacement. It doesn't mean the joint will fail tomorrow, but it means the wear is advanced enough that you should plan the repair within the next few weeks or months, depending on how loud the noise is.

Checking for vibration at highway speed

On a straight highway with light traffic, accelerate to 55 mph and feel whether the steering wheel or the whole car vibrates. Vibration that gets worse as you speed up and improves when you slow down suggests a CV joint problem, though it can also indicate a bent wheel or tire imbalance. Vibration that happens only during acceleration or only when turning is more likely to be a CV joint.

To narrow it down, turn the wheel fully left while driving slowly in a parking lot and feel whether the vibration is worse. If it is, the right CV joint is likely damaged. Turn right and check the left side the same way. Vibration combined with clicking is a strong sign that the joint is worn enough to need replacement soon.

Vibration alone, without clicking, can sometimes mean the joint is damaged inside but the balls haven't worn enough to click yet. Have the vehicle inspected by a mechanic if you feel vibration but hear no noise, because the joint may be close to failure.

What to do if you find a torn boot

A torn boot caught early—before grease has been flung out and water has gotten in—can often be saved by replacing just the boot and regreasing the joint. This is called a CV boot replacement and costs $150 to $300 per side at most shops. The joint itself is left in place and reused.

To know whether the joint inside is still good, a mechanic will disassemble the boot, inspect the balls and races for pitting or scoring, and clean out any water or contamination. If the joint looks clean and the balls roll smoothly, the boot replacement alone will restore the joint. If the joint is already damaged, replacement of the entire axle assembly becomes necessary.

Don't delay on a torn boot. Every mile you drive on a torn boot allows more water and dirt inside, and once the joint is contaminated, it deteriorates quickly. A boot replacement done at 80,000 miles might cost $200. The same joint, left alone until 85,000 miles, might need a full axle replacement at $600.

When to replace the entire CV axle

If you hear clicking that's loud and constant, feel significant vibration, or if a mechanic tells you the joint inside is pitted or damaged, the entire axle assembly needs replacement. Most shops will replace the whole axle rather than rebuild the joint because the labor cost is similar and the new axle comes with a warranty.

Replacement usually takes one to two hours per side. The old axle is unbolted from the transmission on one end and the wheel hub on the other, then a new one is bolted in. Some shops will rebuild your old axle and keep it as a core, which can save $50 to $100 compared to buying a new one outright, but the timeline is the same.

If both front axles are worn, some shops will offer a small discount for doing both at once because the labor overlaps. Ask about this when you get a quote. All-wheel-drive vehicles have rear CV axles too, though they wear more slowly than front ones.

Differences between front and rear CV joints

Front CV joints do most of the work because they handle both steering and power delivery. They wear faster and are more likely to fail first. Rear CV joints, found on all-wheel-drive vehicles, are simpler and usually last longer because they don't have to flex for steering.

The inspection method is the same for both: look for torn boots, listen for clicking during turns, and feel for vibration. Rear joints are harder to access visually, so you may need to get under the vehicle or have a mechanic look. If you drive all-wheel-drive and hear clicking from the rear, have it checked promptly because rear joint failure can affect traction in snow or on slippery surfaces.

Frequently Asked Questions

How often should I check my CV joints?

Check the boots visually every time you rotate your tires, usually every 5,000 to 7,000 miles. Listen for clicking during tight turns at least once a month during normal driving. If you live in a snowy or salty climate, check more often because salt accelerates boot deterioration.

Can I drive with a torn CV boot?

Yes, but not for long. A torn boot will allow water and dirt into the joint, and the joint will fail within a few hundred to a few thousand miles depending on conditions. Have the boot replaced as soon as you notice the tear to avoid a more expensive joint replacement later.

What does a clicking CV joint sound like?

It sounds like a rapid clicking or popping that speeds up as you turn tighter. It's most noticeable during tight parking lot turns at low speed. The sound comes from the outer joint on the side of the turn and gets louder the more the joint flexes.

Can a bad CV joint cause the car not to start?

No. A worn CV joint will cause clicking, vibration, or grease splatter, but it won't prevent the engine from starting. If your car won't start and you also have CV joint symptoms, those are two separate problems.

Is it safe to drive with clicking from a CV joint?

Yes, in the short term. Clicking means the joint is worn but still delivering power. However, a joint that clicks loudly is close to failure and can seize suddenly, which could cause loss of power to that wheel. Have it inspected and replaced within a few weeks rather than months.