Constant Velocity Joint

What is a CV?

a CV (Constant Velocity) is a component used in the front end drive on front wheel or all-wheel drive layouts on the driveshaft. It is used to transfer the rotating power of the driveshaft yet still be able to do this while the drive shaft angles when turning the steering wheel.  This works like a typical U-joint, but the special features of the constant velocity joint is that it does not constantly put stress on the same small parts inside. 

The CV is a simple component and works by an input shaft with splines and an outer race with an output shaft with splines.  The rotating force carries through because the input shaft is connected to a ball cage which has slots to hold the bearing balls inside, and carrying the force over to the outer race.  The use is that the output shaft can still carry out the rotating force and still angle to the input shaft.  This has many advantages over a universal joint including higher angles and more even wear between internal parts, but they still do wear out (like all other parts).  They need to at least be checked time to time.  Usually they will wear out when the car is running on a broken CV boot for too long.  This is because if the boot is not replaced in time,  water, moisture and dirt can come in and damage the internal parts.   Make sure to check the boots from time to time.   A tradesman will notice broken boots when you get your warrant of fitness.

Servicing the CV:

Servicing the CV boot requires removing the drive shaft from the car.  Refer to my previous blog post on CV boots.

When the drive shaft is removed, remove the CV boot.  This will require cutting the clamps and the rubber boot itself.  Wipe as much grease off as you can.   Move the output shaft around and notice the smoothness of the movement.  Give it a wiggle, it shouldn't knock around.  Hammer off the outer race from the driveshaft with a slide hammer.  You will need to use the center wheel nut.  Do not lose this part.  After the outer race is removed,  clamp it on a vice clamp. 

The balls need to be removed.  Tap the inner race down and remove the balls from the opposite side.  Once all the balls are out, the inner race can be removed along with the ball cage. Simply locate the larger rectangular ball slots and align them with the walls of the outer race and pull out the inner race.  the ball cage can be pulled out.

inspect the individual inner components.  Look for any damage including dents, rust, ovality in the balls, uneven wear of the balls.  Inspect the splines for and dents, the threads and the circlip grooves.

If any of the parts are a failure,  The CV joint will need to be replaced.  If you are replacing the joint,  make sure to compare the old and new joint side by side.  If in doubt, do not replace.