What Is the Purpose of a CV Joint?

CV, or constant velocity, joints are an essential component of front-wheel-drive cars. They are built into the front axle of cars and, on occasion, can be found on rear axles as well. They join the main drive axle to the shaft attached to the front wheels. Their purpose is to efficiently and continuously transfer power from one side of the shaft to the other, at a range of angles. They are near the front wheels and are protected by black bulbous rubber boots filled with MoS2 grease. To find them, look under the front wheel wells.

The first CV joints were invented hundreds of years ago. One of earliest was used in the transmission of a Strasbourg Cathedral clock tower built in 1351, according to "Universal Joints and Driveshafts: Analysis, Design, Applications." It effectively moved the hands of the clock at angles to the driveshaft. Today, major companies such as the GKN Group in Birmingham, England, and Lohmar, Germany, produce them for cars. New ideas and designs for CV joints are always in the works.

As a driver turns the steering wheel, the angle formed across the CV joint changes, yet power is smoothly and continuously delivered to the wheels. It is the design and work of the CV joint that allows for this smooth and constant delivery of energy to the wheels regardless of the angle at which the driver is turning. The CV joint is also an integral part of the suspension. The joints enable power delivery to the wheels even as they bounce up and down along the terrain.

CV joints must transfer power efficiently; otherwise, energy would be lost and gas mileage would plummet. Efficiency is created through a number of designs employing precision-made components. The design theme of CV joints employs a ball-and-socket structure with bearings.

CV joints are needed for steering and usually last a long time; however, if the rubber boot surrounding the CV joint should get damaged, the joint probably won't last much longer. Dirt and debris from the road get into the joint and begin scraping the bearings. Next, the bearings lose their shape, further damaging the joint. Finally, the telltale clicking sounds come with each turn.