How Does A CV Axle Work
All front-wheel-drive cars have Constant Velocity joints, or CV joints , on both ends of the drive shafts (half shafts).
The CV joints are needed to transfer the engine power regardless of the turning angle from the transmission to the drive wheels at a constant speed while accommodating the up-and-down motion of the suspension. In front-wheel-drive cars, CV joints deliver the torque to the front wheels during turns. There are two most commonly used types of CV joints: a ball-type and a tripod-type. In front-wheel-drive cars, ball-type CV joints are used on the outer side of the drive shafts ( outer CV joints ), while the tripod-type CV joints are mostly used on the inner side ( inner CV joints ).
Inner CV joints connect the drive shafts to the transmission, while the outer CV joints connect the drive shafts to the wheels. Many rear-wheel-drive and four-wheel-drive cars, as well as trucks, also have CV joints.
Early front-wheel-drive systems such as those used on the Citroën Traction Avant and the front axles of Land Rover and similar four-wheel-drive vehicles used universal joints, where a cross-shaped metal pivot sits between two forked carriers. These are not CV joints as, except for specific configurations, they result in a variation of the angular velocity. They are simple to make and can be tremendously strong and are still used to provide a flexible coupling in some prop shafts, where there is not very much movement. However, they become "notchy" and difficult to turn when operated at extreme angles.
As front-wheel-drive systems became more popular, with cars such as the Mini using compact transverse engine layouts, the limitations of universal joints in front axles became more obvious. Based on a design by Alfred H. Rzeppa, constant velocity joints solved a lot of these problems. They allowed a smooth transfer of power despite the full range of angles through which they were bent.
Generally, the CV joint can work for a long time, provided it is maintained properly. A malfunctioning CV joint will result in a drop in engine power being transmitted to the vehicle. There are a few causes of CV joint failure.
Symptoms of a Damaged CV Joints
The most common problem with the CV joints is when the protective boot cracks or gets damaged. If it happens, the grease comes out, and moisture and dirt get in, which causes the CV joint fails due to lack of lubrication and corrosion.
If you notice CV joint boot damage early, it will help you to protect the CV joint from corrosion. It’s very easy to repair it, simply replacing the boot and repacking the CV joint with a fresh grease is all that is usually needed.
Signs of a Damaged CV Joint
Grease is coming out of a small crack or tear. If the damage is bigger, you might see dark oil splattered on the inside of the wheel rim and around the area inside of the drive wheel.
A clicking or popping noise when turning. If it becomes louder when accelerating in turns, it can be the case of outer CV joint damage.
Lack of lubrication in the CV joint can cause to the CV joint damage, this you can notice when you hear a humming or growling noise. If you feel a steady knocking while driving at low speeds, this is a sign of CV joint failure as well.
If it becomes difficult when making turns or while rounding a corner, it can also be because of a failure of CV joint.
If you feel your vehicle shaking when accelerating, it can cause a fault in the inner CV joints.
A CV joint doesn't need any maintenance and can work very long, as long as the protective CV joint boot is not damaged. If it’s damaged, replace the boot and fill the right amount of grease. If a CV joint itself is worn out, it cannot be repaired; it will have to be replaced with a new or reconditioned part. Because of that, we recommend checking your vehicle’s CV joints in every regular maintenance.