CV Axles-Description and Replacement Info

For most of you that have worked on a front wheel vehicle the image you see below is nothing new, but for the people out there that have never seen one of these things before, it is called a CV ( Constant Velocity ) axle or more commonly known as a Half Shaft.

A CV joint or constant velocity joint is a type of mechanisms that connects two fixed rotating shafts. This joint allows the shafts to be connected while axis’s pivots change, for example when suspension or steering operation occurs. CV joints are widely used in front-wheel and rear wheel drive cars.

CV joints can deliver torque more evenly then conventional “U” joints. The CV joint is used because of its ability to transmit more even torque throughout a particular flex range. A CV joint can also deliver power on a wider range of angles then “U” joints which makes them more desirable then its older counterpart.

The CV joint is virtually non-serviceable unless the boot ruptures or extreme conditions exist, like high mileage or abuse. When the CV joint fails simply replace it with a new unit.

A CV Half Shaft is composed of four basic pieces. They are the inner joint or inboard shaft , the outer joint or outboard shaft, the axle and the axle nut. Both inner and outer joints have a protective rubber boot on them that can sometimes tear, which is why most half shaft fail in the first place.

If you were to open the inner and outer joints up, chances are they would look like this on the inside. There are those who like to rebuild the joints and replace the boots but due to economical reasons, I prefer to replace them.

For those of you that are curious as to why I say that, I have a few illustrations below that give you the very basics of Boot Replacement.

The Boot itself is very inexpensive but when it fails the entire half shaft is prone to fail as well. The job of the Boot is protect the bearing assembly inside from the outside elements while holding in life giving grease.

The Boot closest to the wheel is always prone to tear or split first due to them experiencing the most movement.Once the boot tears or splits, 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.

If you own a front wheel drive vehicle, look under it and check out your boots for signs of tearing . It should be easy to spot. If so, then its only a matter of time before the fail. Once they fail, your vehicle will no longer move in any direction.

The most common sign that your CV joints are about to fail is by the clicking sound they make when you make a turn. You only have a short while before you the bearing fail and the shaft is no longer connected to the outboard joint.

Removing the Half Shaft Assembly :
The job of removing the Half shaft on most cars is pretty much the same on all cars. Below is a quick list of how to do it, but please consult your repair manual for a more complete guide to replacing your own half shaft.
1. Remove the front wheels
2.Remove the big nut that holds the joint to the wheel hub. ( You may have to replace it with a new one on some models )
3.The steering knuckle ( Thats where the brake hardware bolt to ) must either be loosened at the strut mount or at the lower ball joint to allow the shaft to slip out of the hub assembly. You choose which one is easier.
4.The inner or inboard joint will be held into the transmission by either bolts or by a retaing clip called a circlip. ( Refer the the illustration above)
5. If you see no bolts then you will have to pry the half shaft out the transmission due to the cir clip holding it in there. Be careful not to damage the transmission while doing this. Try using a slide hammer with a CV joint puller attached ot the other end. It works pretty good.

6. Install the new shaft in the reverse. Grease the splines ( Grooves on the shaft with the large nut ) and lubricate the seal in the transmission first. I would replace the seal if you are this far into it, its easier with the shaft out.
7. Use new hardware like cotter pins and axle nuts. Torque the axle nut to spec with the vehicle on the ground. You can find the Torque Spec to the axle nut or CV joint bolts in any Haynes or Chilton Manual .
If you don’t have a manual you can log onto www. alldata.com and for a subscription fee you can have all of your vehicles info for one year.

Well that’s about it. I hope this has answered a few questions for you on CV Half Shaft and hopefully taken the mystery out of how they work. If you like this article then please send it to a friend and let them know about us or if you have a question, then please leave me a comment by clicking on the contact tab at the top of the page.

Until next time, this is Jeff Williams saying ” Thanks for stopping by ” and if this article has been helpful to you then please click on the coffee cup icon and help keep this site running. Thanks.   Jeff

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