An axle is used to propel a vehicle's wheels by transmitting power from the transmission. Each axle has two constant velocity (CV) joints, that are packed with grease and encapsulated by a constant velocity (CV) boot. If the CV boot becomes damaged then dirt and moisture can get into the boot which will cause the grease in the CV joint to leak out. If there is no grease to lubricate the CV joint, then the joint will become worn. Then a CV boot and joint replacement is necessary. If the damaged CV boot is caught early, then it can be replaced without having to replace the CV joints.
To perform a CV boot and joint replacement, the technician removes the wheel and disassembles the suspension to the point where the axle can be withdrawn from the transmission. The axle is cleaned and disassembled and the new CV joint is fitted and the new CV boot is installed. Then the axle is reassembled, installed, and the suspension is reassembled.
Most manufacturer factory warranties cover a CV boot and joint replacement under the powertrain warranty portion. For extended coverage of the CV boot and CV joints, and extended auto warranty is an option that will extend coverage beyond the expiration the factory warranty.