What a CV axle does and why it fails

A CV axle (constant velocity axle) is the shaft that connects your transmission to your wheel, letting power flow from the engine while allowing the wheel to turn and move up and down. On front-wheel-drive cars, you have two CV axles—one on each side. On rear-wheel-drive cars, the rear axles work differently and are not CV axles.

CV axles fail because the rubber boots that protect the joints crack or tear, letting grease leak out and dirt get in. Once that happens, the joint wears out and the axle becomes damaged. You might notice a clicking sound when turning, vibration at highway speeds, or a clunking noise when accelerating. A damaged CV axle should be replaced before it breaks completely, which can leave you stranded.

Replacing a CV axle is a job many people with basic mechanical skills can do at home, though it requires getting the car safely off the ground and having the right tools. If you are not comfortable working under a car or do not have the tools, a mechanic can do it in one to two hours per side.

Key Takeaways

  • A CV axle connects your transmission to your wheel and fails when the protective rubber boot tears, letting grease escape and dirt enter the joint.
  • You will need a jack, jack stands, a socket set, a pry bar, and possibly a CV axle puller tool, depending on how stuck the axle is.
  • The basic steps are: lift the car, remove the wheel, unbolt the axle from the transmission and wheel hub, slide it out, and install the new one in reverse order.
  • If the axle is stuck or you do not have a lift, a mechanic can replace one side in about an hour for a cost that varies by vehicle and location.

Tools and equipment you will need

Before you start, gather the tools. You need a floor jack and at least two jack stands rated for your car's weight—never work under a car supported only by a jack. You also need a socket set (usually 10mm to 21mm depending on your car), a wrench set, a pry bar, and a hammer or rubber mallet. A CV axle puller is helpful if the axle is stuck, though you can sometimes work around it with a pry bar and patience.

Some cars require a special tool to remove the axle nut or to separate the ball joint. Check your vehicle's service manual or search online for your specific year, make, and model to see what tools are called for. If you do not have a manual, many auto parts stores will lend or rent specialty tools for a small deposit.

You will also need new cotter pins (the small split pins that lock the axle nut) and possibly new bolts, depending on whether your car reuses them. Buy these when you buy the replacement axle. Wear safety glasses and work gloves.

Steps to remove the old axle

Start by loosening the axle nut (the large nut at the center of the wheel) while the car is still on the ground—it is very tight and easier to break free before you lift. Then lift the car with the floor jack under the frame, and place jack stands under the car's support points. Lower the car onto the stands so it rests on them, not the jack.

Remove the wheel. Unbolt the axle nut completely and set it aside. Next, locate where the axle connects to the transmission (the inner end) and the wheel hub (the outer end). Unbolt the axle from the transmission—this is usually two or three bolts. If your car has a ball joint connecting the steering knuckle to the lower control arm, you may need to separate it using a ball joint separator tool or by unbolting it.

Once the bolts are out, the axle should slide out of the transmission. If it is stuck, tap it gently with a rubber mallet or use a pry bar to work it free. Be patient—forcing it can bend the axle or damage the transmission seal. Once the inner end is free, pull the outer end out of the wheel hub. The axle should come out as one piece.

Installing the new axle

Before you install the new axle, check that the rubber boots are intact and the joints move freely. Slide the outer end into the wheel hub first, then guide the inner end toward the transmission. You may need to angle the axle to fit it in—this is normal. Once both ends are roughly in place, bolt the inner end to the transmission and tighten the bolts to the torque specification in your manual (usually 30 to 50 foot-pounds, but check your car).

Next, bolt the outer end to the wheel hub and install a new axle nut. Tighten the nut by hand first, then use a socket and breaker bar to tighten it fully. The torque is usually 150 to 200 foot-pounds depending on the vehicle—do not guess. If you do not have a torque wrench, many auto parts stores will tighten it for you for a small fee. Install a new cotter pin through the hole in the axle nut to lock it in place, bending the pin's ends to hold it.

Reinstall the wheel, lower the car onto the ground, and tighten the wheel lug nuts in a star pattern (opposite sides alternately) to seat the wheel evenly. Take the car for a short test drive to make sure there are no noises or vibrations.

When to take it to a mechanic instead

If the axle nut will not budge even with a breaker bar, or if the axle is so corroded it will not slide out, a mechanic has power tools and experience to remove it without damage. If you do not have a torque wrench and cannot borrow one, a mechanic should tighten the axle nut to spec—getting this wrong can cause the wheel to loosen or the bearing to fail.

If your car has electronic power steering, all-wheel drive, or a complex suspension, the job may require disconnecting sensors or removing additional components. Check your manual before you start. If the work looks beyond your comfort level, a mechanic is the safer choice. Most shops charge between $300 and $800 per axle depending on the vehicle and your location.

Preventing CV axle failure

The best way to avoid replacing a CV axle is to catch a torn boot early. During routine maintenance, look at the rubber boots on both sides of the axle (they look like accordion-shaped covers at the joints). If you see grease splattered on the inside of the wheel or a visible tear in the boot, have it inspected. A mechanic can sometimes replace just the boot and repack the joint with grease, which costs far less than replacing the whole axle.

Avoid hard cornering and aggressive acceleration, which put stress on the CV joints. If you hear clicking when turning, have it checked soon—that is often the first sign of joint wear. Regular wheel alignments also help, because a misaligned wheel puts extra load on the axle.

Frequently Asked Questions

Can I drive on a bad CV axle?

You can drive short distances, but not safely for long. A failing axle will eventually break completely, which can cause you to lose power to that wheel suddenly. If you hear clicking or feel vibration, have it inspected within a few days and avoid highway speeds until then.

Do I have to replace both axles at the same time?

No. Replace only the one that is damaged. However, if one axle has failed from age or wear, the other side may not be far behind. Some mechanics recommend replacing both if the car is older, but it is not required.

What is the difference between a rebuilt and a new CV axle?

A rebuilt axle has been disassembled, cleaned, and reassembled with new joints and boots. A new axle is manufactured fresh. Rebuilt axles cost less but may have a shorter lifespan. Most come with a warranty of one to three years. New axles cost more but typically last longer.

How long does a CV axle last?

A CV axle typically lasts 80,000 to 160,000 miles if the protective boots stay intact. If a boot tears early, the axle may fail in 10,000 to 20,000 miles. Regular inspection and catching a torn boot early can extend the life significantly.

Do I need to align my wheels after replacing a CV axle?

Not usually, unless you disconnected the ball joint or steering components during removal. If you only unbolted the axle from the transmission and hub, alignment should not be affected. If you are unsure, a quick alignment check costs little and gives peace of mind.