A half shaft—also called an axle—transmits power from the transmission to propel the vehicle's wheels. Each half shaft has two constant velocity (CV) joints, which are packed with grease and encapsulated by a rubber cover known as a CV boot. The integrity of the boot is critical to the life of the CV joint. Torn or cracked boots will allow dirt and moisture in, which causes the lubricating grease to leak out. Failed boots should be repaired immediately.
A clicking sound (that increases with the speed at which a vehicle takes a sharp turn) strongly suggests that a half shaft is worn and in need of replacement.
To replace the CV boot cover, the wheel is removed and the suspension is disassembled to the point where the half shaft can be withdrawn from the transmission and suspension. The new CV boot is installed and the suspension reassembled.