The front halfshafts are used to couple the transaxle to the road wheels. This allows power to be delivered as the suspension moves up and down and while the wheels are turned side to side to negotiate turns. In order to accomplish the ability to simultaneously supply rotational power and the ability to change direction, an axle must have a component that can pivot and rotate at the same time.
This is accomplished by using a halfshaft with an inner and outer Constant Velocity (C/V) joint. In order to lubricate the CV joint, the joint is assembled using approved high-temperature molybdenum disulfide grease capable of withstanding extreme pressure and heat. The grease is retained in the CV joint by a tapered accordion boot, which is installed over the axle and the CV joint.
The CV boot allows the CV joint to rotate and pivot, while retaining the lubricant and protecting the CV joint from water and debris.
A torn, damaged or leaking CV boot should be replaced immediately. Loss of lubricant will cause the joint to overheat and damage it. Because these are precision-machined components, they can be quite expensive to replace. The cost of the boot is about 10-20% of the cost of a CV joint.
Typically a failed CV joint makes a clicking noise during acceleration, especially when accelerating from a stop and turning.