A CV boot is a black, accordion-like piece of rubber that covers the constant velocity joint of a car that has front-wheel or four-wheel drive. There are two CV boots on a front-wheel-drive car.
A CV boot covers and protects the drive-axle joints that allow a car to turn right and left and to go forward or backward with its front wheels. They hold the grease that keep the joints lubricated and operating smoothly. Replacing a worn, cracked CV joint is a relatively easy and inexpensive repair. However, mechanics often recommend replacing the entire drive axle instead of repairing the individual CV joint.