Changing CV (Constant Velocity) axles today is almost as common as doing brake jobs. But some CV axles can be pretty stubborn to remove. In this article learn some of the tricks I've used over the years as a Master Tech to make changing CVs and 1/2 shafts easier. Automotive specialty tools are sometimes needed to make the job easier, I'll discuss some of those and if it is better to replace the entire half shaft, the joint or just the CV boot.
Clicking On Turns
Since you're reading this you may already know that a common sign of a bad CV joint is popping and clicking on turns. A shudder on straight take offs could be a worn inner joint, but this is much less common. Outer joints have the most movement (like on turns), that's why outer boots usually wear more than the inner ones. CV boots are designed to pump grease through the joint during movement. Wear that causes outer joints to make noise can be accelerated if the CV boot breaks from dry rot or wear and the lubricating grease is lost. If the CV boot breaks, grease is thrown out of the joint by centrifugal force while driving. Without grease to keep the joint lubricated and cooler, its life is drastically reduced. Also outside elements like moisture and dirt can enter the joint, further reducing its life expectancy. Once they wear, they make a clicking noise upon turns while accelerating. If they are noisy, the 1/2 shaft assembly may be the easiest way to go instead of replacing just the joint. CV 1/2 shaft prices have come down in the last decade and are more readily available than they used to be.
Removing the Half Shaft Assembly
The job of removing half shafts on most cars is mostly the same.
- Remove the big nut that holds the joint to the wheel hub.
- It may be necessary to unbolt or un-clip the brake hose to prevent stretching it when removing the axle.
- The steering knuckle (where the brake rotor mounts), must either be loosened at the strut mount or at the lower ball joint to allow the shaft to slip out of the hub. Choose the easiest!
- The inner CV will either be held into the transmission by bolts or with a retaining clip (the clip is not visible).
- If there are no bolts on the inner joint, in most cases it will need to be pried out with a pry bar.
- Alternately a slide hammer with a CV joint puller can be used to remove the inner joint from the transmission.
Inspecting and Replacing Boots
You may be able to detect and replace worn boots before damage is done to the CV joint. If the boot has dry rot and is about to crack or has just recently split. And the CV joint does not make any noises yet, it has been done in time. The CV half shaft assembly can be removed and just the boot can be replaced with new grease of course. The CV boot kit also comes with two clamps and special grease. It is less expensive to re-boot a joint, but it is a little more labor intensive. On cars that I was familiar with, many times I changed the CV boot without taking the shaft completely out of the car. Usually though, the shaft is removed and placed in a vise to be worked on. The old boot is cut away to help reveal what type of retaining clip is holding the joint onto the 1/2 shaft.
When a cleaner is used, like brake clean and the joint is angled it's easier to see the clip. The joint may need to be turned while kept on an angle to see the clip. Most either require lock ring pliers to spread the lock ring or the joint can be stuck sharply with a hammer (care must be taken not to damage the cage). If you have doubt on what type of retainer you are working with, consult a service manual for your specific model. Be aware that the ball bearings can fall out when the joint is off the shaft and the cage is turned sideways depending on the type it is. After cleaning and drying with compressed air, the grease bag can be cut on the corner and the grease is squeezed into the center of the joint. It's common to force out some of the old grease that was trapped while doing this. Scoop up and discard the old grease that may ooze out. Put the boot and joint back on the shaft by spreading the clip or tapping lightly with a brass hammer. Special CV joint boot clamp tools will be needed to tighten the bands properly. There are two basic types of clamps. There is a type that will be crimped with boot clamp pliers. The other type requires a banding tool, this type is wound and cranked tight using the same motion as you would with a can opener.
A common mistake is damaging the output seal in the transmission when removing or re-installing the axle. If the seal is damaged, transmission fluid will leak. Be careful to center the inner joint when putting it back in. Also a mistake that is made even by professionals is to either break the cir-clip that holds the axle in the transmission or to not install the axle completely IN. It is normal to feel a little movement in and out when pushing and pulling the inner joint when it is properly installed. If the retaining clip is broken or not fully inserted, the shaft can slip out enough that the car will not move! Also if tapping the shaft back into the transmission, be careful not to damage the outer threads. Remember if this is your first axle job, do not hesitate to have a buddy with experience on call!