CV boot

Found in all front-wheel-drive and many rear-wheel-drive cars, constant velocity joints (CV joints) transfer torque from the Drive shaft 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.