Wondering what happens to your car when the CV boot is replaced? Looking for an overview or tutorial because your considering doing a CV boot repair yourself? This may be the page you’re looking for.
WHAT IS A CV BOOT?
Let’s start with the basics. A CV boot is a flexible rubber boot which protects the CV joint. What’s a CV joint? It’s a flexible joint found on both ends of the drive axle. The outer joint allows the front wheels to turn and move up and down. The inner joint allows the suspension to move and the axle to telescope in and out. The CV joints are packed with grease. The CV boots protect the joints. They keep the dirt and grit out and the grease in.
HOW IS A CV BOOT REMOVED FROM A CAR?
The first step is to remove the axle from the car. The axle nut will usually be staked in place as a safety measure. It’s best to de-stake the axle nut before removing it. Some axle nuts are so beefy that they’ll tear up the threads on the way off. KTC (the Japanese equivalent to Snap-On) makes a great de-staking tool that makes the job a lot easier. You can purchase this and other KTC tools at thetoolnetwork.com
HOW DO YOU REMOVE THE CV JOINT FROM THE AXLE?
Once the axle has been removed, we put it in a vice. This makes is a lot easier to work on the axle. If the axle is rolling around on the bench, it’s a lot harder to deal with the clamps and clips.
WHAT’S THE BEST BRAND OF CV BOOT?
When possible we like to use genuine CV boot kits. This kit from Toyota comes with all of the boots, grease, clamps, and clips necessary for the job.
HOW DO YOU REMOVE THE OUTER CV JOINT?
Some axles have removable outer CV boots, but the Prius does not. To replace the outer CV boot, the inner joint and harmonic dampener must be removed, then the old boot can be removed and the new boot can be installed by sliding it down from the opposite end of the shaft.
The inner joint is indexed to the shaft with splines cut into both the shaft and the tripod joint. A circlip holds the joint in place.
Once the circlip is removed, the inner joint slides off, followed by the damper, then the outer boot.
HOW SHOULD YOU CLEAN THE CV JOINT?
Once the boots are removed, we can start cleaning. I’m not a fan of using a solvent tank to clean the joint for two reasons. First, this can introduce dirt into the joint, and since the joint cannot be disassembled, there’s no guarantee any dirt introduced can be flushed out. Second, solvents used for tanks does not evaporate easily, so some will remain in the joint and dilute the grease. If the boot was mostly whole and there is no road grit in the joint, wiping the old grease off is the best option. If gritty, the best option is a flush with brake cleaner. Brake cleaner is clean, unlike solvent in a tank, and it evaporates quickly so dilution is not an issue.
WHAT KIND OF GREASE SHOULD YOU USE FOR THE CV JOINT?
Here’s something you won’t get with aftermarket CV boot kits: Toyota uses different types of grease for the inner and outer CV joints. Presumably the engineers had a reason for this, so we like to use the grease they specified. When we buy the kits from a Toyota dealer, all of the parts — the boots, clamps, clips, and even the grease the car had when it was new.
HOW DO YOU MAKE SURE THE GREASE GETS INTO THE CV JOINT?
The joint should be “packed” with grease, meaning the grease should be pushed deep into the joint, not just smeared on top. This is accomplished by “slapping” the grease into the joint by hand to push it past the ball bearings. It’s a very messy job. Once the joint is packed, the remaining grease is piled in a mount atop the joint.
HOW DO YOU CLAMP A CV BOOT?
The new CV boot is then clamped in place. Setting the axle in the vise vertically makes it easier to install and clamp the boot because the joint isn’t flexing. Otherwise you’ll have to fight the boot tension while installing the clamps. You may have noticed that the vise jaws are made of aluminum, so clamping down on the splines won’t injure the joint.
The inner CV boot is positioned on the axle shaft first. Then the joint is packed with grease and pushed onto the inner tripod. Once the joint is in position, the boot is slid onto the joint and clamped in place.
Here’s the completed axle — ready for installation and years of continued service.