CV Axles and Boots

The common complaint of an unfamiliar sound coming from under a vehicle in for repairs often leads you to discover a worn or failed rubber boot. Most suspension parts rely heavily on good lubrication, and good lubrication must be contained and protected by a rubber boot within its working cavity. Sometimes you only need a small boot with minimal amounts of grease – because the movement is small. However, in the case of a CV axle, large amounts of grease must be held in the cavity as the boot is subject to a wide array of movement and angles.


CV axles are a part of the drivetrain that transfers power from the engine to the wheels. They are most commonly found on a front-wheel-drive vehicle, however, CV axles can also be found on independent rear suspensions on rear-wheel-drive vehicles.


The axles receive rotational power (or torque) from the engine drive shaft and transfer it directly to the hub, thus the name Constant Velocity axle. Each CV axle drives a single wheel, so a pair is always required.


You will find in most vehicles that one CV axle side is shorter than the other, typically the driver’s side and a longer shaft on the passenger side. You should identify the longer shaft first as this typically is going to be the side that fails first. Since this shaft is longer, more force is applied to it, and as a result, it tends to wear quicker. Once the weak side begins to wear, it directly affects the other side. It is recommended when a CV axle is worn, to always replace them in pairs so there is no imbalance to the vehicle’s suspension and ride control.


Because CV axles are the direct link between the engine and the wheels, they are subject to high levels of stress over time and will eventually wear out. When they do wear out, the CV axles usually will produce a few symptoms that can alert the driver that they require attention. There are two common areas on the CV axle that will be most affected by wear: the first is within the outer joint housing and the second is inner joint spline damage.