Found in all front-wheel-drive and many rear-wheel-drive cars, constant velocity joints (CV joints) transfer torque from the driveshaft to the wheels and permit the vehicle suspension system to move up and down without the passengers noticing each bump. CV joints are protected by plastic or rubber boots that hold in the grease the joints are packed in. If the boot fails, dirt and moisture displace the grease, impairing the joint. Inspecting the CV boots at the first sign of trouble can help save the CV joints and money in repairs.
Damaged CV boots should be replaced promptly, as the CV joint can be ruined in just a few days, particularly in wet weather. However, if you hear a popping, clicking, humming or growling before you find the CV boot has been damaged, the joint is already ruined and needs to be replaced along with the boot.