Should you replace a CV boot versus new axle shaft

In most cases, it’s best to install a new or rebuilt axle shaft instead of just a new boot

Replacing a CV boot and replacing an axle are two different repair options for addressing issues related to a vehicle’s constant velocity (CV) joint. Here’s a brief explanation of each:

What’s involved in replacing a CV boot

Remove the axle from the vehicle

To replace a torn CV boot you must first disconnect the axle shaft from the wheel hub. Most technicians prefer to remove the entire half shaft from the vehicle before replacing the boot because you have to remove the CV joint in order to replace the boot. Removing the outer CV joint can require removing a snap ring or using a punch and hammer to remove the joint. That’s often easier to do when the axle is held in a vice.

Remove the CV joint from the axle and clean out the grease

The inner “spider” joint is held on by a snap ring, while the outer CV joint is held in by a circlip or a snap ring. Once you remove the joint from the axle shaft, you have to clean out all the grease so you can inspect the CV joint. A torn boot allows road grit to get into the joint and that grit can often damage the joint.

Once the CV joint is clean, you can install the new boot and reinstall the joint

Slice the boot onto the axle shaft, then reinstall the inboard spider and bearings and the outer CV joint. Move the new boot into position and secure one end of the boot with the clamp provided in the kit.

Clean all old grease from the joint before adding the new boot

Add grease to the new boot and burp the air out of the joint

Each boot kit comes with a packet of grease specially designed for CV joints. Do not use ordinary chassis grease. Clip a corner of the grease packet and the squeeze all the grease into the boot, avoiding grease on the boot where it seals. Install the clamp. Then reinstall the axle shaft into the vehicle

Why it usually makes more sense to replace the entire axle shaft versus replacing just the CV boot

There’s likely already some damage in the joint

If the CV boot is torn, chances are high that the joint has already been contaminated with road grit. You simply don’t know the condition of the joint at this point. If you do the work yourself or pay a shop to replace just the CV boot, you could wind up with CV joint vibration or noise due to the internal wear caused by running with dirt and grit in the joint.

It’s labor intensive to replace just the boot

Most shops remove the entire axle shaft before removing the joint and installing a new boot. The CV boot kit is cheap, but there’s more labor involved to replace the boot than to replace the entire half shaft.

With a rebuilt axle shaft or a new axle shaft you get a warranty

No shop will warrant the joint if you insist on just a CV boot replacement instead of replacing the axle shaft. Some shops refuse to reboot a CV joint for this reason.

What is a CV joint?

A constantly variable CV joint transmits power at a variable angle and at constant rotational speeds. It’s used in place of a traditional U-joint because it can transmit rotational power at greater angles; that’s important in a front wheel drive vehicle where the wheel have to turn.

Ford engineer Alfred Hans Rzeppa designed the CV joint in the 1930s. Instead of four U-joint bearings mounted in two yokes, Rzeppa used six balls mounted in paths. His invention was used widely in WWII Jeeps’ front axles.

What is a CV boot and how does it fail?

A CV boot is a rubber cover that protects the CV joint, which connects the drive axle to the wheel. It keeps grease inside the joint and debris outside. Over time, the constant flexing can cause the CV boots to crack or tear, allowing dirt and moisture to enter the joint and grease to escape. This can lead to CV joint damage.

©, 2023 Rick Muscoplat