CV Axle Replacement: Clicking, Torn Boots and What to Expect

What is a CV axle and what does it do?

A CV axle is the shaft that carries power from the transmission out to a wheel. MOOG, a steering and suspension parts maker, explains that CV stands for constant velocity: the axle keeps the wheel turning at a steady speed even as the suspension moves up and down and the wheels steer. You may also hear it called a half shaft or axle shaft.

How many you have depends on the drivetrain. According to MOOG, a front-wheel-drive car has two (one per front wheel), an all-wheel-drive vehicle has four, and some rear-wheel-drive vehicles with independent rear suspension have them too.

Each axle has two flexible joints: an inner joint at the transmission end and an outer joint at the wheel end. Both are packed with grease and covered by a ribbed rubber boot. The boot is the weak point. Once it splits, the joint starts to wear.

What are the signs you need a CV axle replacement?

MOOG lists four common signs of a failing CV axle:

• Clicking or popping when turning. Usually from a worn outer joint, and often loudest on tight, slow turns such as parking lots, especially under throttle.
• Grease on the inside of the wheel. A torn boot flings grease around the inside of the wheel and nearby parts.
• Clunking when accelerating or slowing down. More often linked to the inner joint.
• Vibration. A shake that grows with speed can come from a worn axle.

A torn boot on its own is an early warning. MOOG explains that when the boot ruptures, the joint loses grease and water and debris can get in, which speeds up wear. Some owner’s manuals list the boots as a regular inspection item; Mazda’s CX-5 maintenance schedule, for example, includes inspecting the driveshaft dust boots.

Other parts can make similar noises. A clunk over bumps can be a ball joint or sway bar link, and a hum that changes with speed is more typical of a wheel bearing. Our guide to a clicking noise when turning helps sort the sounds out.

Boot or whole axle: which gets replaced?

If a split boot is caught early, before the joint is noisy, replacing just the boot and repacking the joint with fresh grease can be an option. Once the joint clicks, clunks or vibrates, the wear is already done, and a complete replacement axle is the usual fix. The mechanic decides based on how long the boot has been torn and what the joint feels like.

You may also be offered both sides. MOOG says many technicians recommend replacing the left and right axles at the same time, because both have worked under the same conditions. That is a judgment call, not a rule; ask the mechanic to show you the condition of the other side.

Can a mobile mechanic replace a CV axle in the driveway?

Often, yes. On most front-wheel-drive cars, a front CV axle is a common mobile job that needs a flat, firm surface, a jack, jack stands and hand and power tools. See what a mobile mechanic can and can’t do for the general limits.

Some jobs are harder away from a shop:

• Seized parts. Rust can lock an axle into the wheel hub, and freeing it can take more time and tools.
• All-wheel drive and trucks. Rear axles, and axles on some four-wheel-drive trucks, can involve more disassembly.
• Alignment. Axle replacement often means separating suspension or steering parts to make room. Ask whether an alignment check is recommended afterward on your vehicle. Alignment itself needs an alignment rack, which is shop work.
• Parking rules. The car will be raised with a wheel off, so apartment lots and HOAs may not allow it. Check first.

What does the job involve?

1. Inspection. The mechanic confirms which side and which joint is at fault, often with a short drive and a look at the boots and axle play.
2. Quote. You get a price for the axle, or boot kit, and labor before work starts. Ask for a written estimate.
3. Raise and support the car. The car goes up on a jack and is set on jack stands, and the wheel comes off. No one should work under a car held up by a jack alone.
4. Remove the old axle. The axle nut is removed and the suspension is separated enough to slide the axle out of the hub and pull it from the transmission.
5. Fit the new one. The new axle goes in, everything is reassembled and tightened to the manufacturer’s specification, and any transmission fluid lost is topped up.
6. Test drive. The mechanic checks that the click, clunk or vibration is gone.

This is not a job to try with only the car’s spare-tire jack. If you want to watch, stay clear of the car while it is raised.

How much does CV axle replacement cost?

CV axles are not in this site’s standard price table, because the price swings with the vehicle, the side, whether it’s a boot or a full axle, and the part chosen. The mechanic quotes after looking. These related ranges from the site’s price table, based on prices that mechanics we list publish on their own websites, still apply:

Ask whether the quote is for a new or remanufactured axle, and whether it is an OEM or aftermarket part. Remanufactured parts may carry a core charge, so check whether the quote accounts for it. See mobile mechanic cost for the full table.

What should you ask before booking?

• Is it the outer joint, the inner joint or just the boot, and which side?
• Do you recommend replacing one axle or both, and why?
• Is the part new or remanufactured, and what warranty covers parts and labor?
• Will my car need an alignment check afterward?
• Can you do it where the car is parked, or does it need a shop?

A mechanic who can see the car will know more than any guide. Noises travel through a car, so the side you hear it from is not always the side with the problem.

What to do next

If you hear clicking on turns or see grease inside a front wheel, have it checked soon, before a torn boot becomes a worn joint. Find a mobile mechanic in your city, or send a request with your year, make, model and drivetrain, where the car is parked, and when you hear the noise.