A constant velocity joint is a coupling that connects two rotating shafts, an input shaft and an output shaft, at an angle. A constant velocity joint, by design, ensures that both the input and output shaft rotate at the same speed, regardless of the angle of the joint. For example, constant velocity joints connect the drive shafts on front or all-wheel drive cars to the front wheels, allowing the wheels to steer while being powered.
Constant velocity joints also connect drive shafts to non-steering wheels, allowing the wheels to be properly driven across the full range of cars' suspension travel. To fulfill different applications, constant velocity joints come in a variety of designs, including fixed-ball, ball and tripod types. Certain types are better for greater overall mobility, while others are more suited for operation at a particular angle. Additionally, plunging constant velocity joints can move laterally as well as axially.
Constant velocity joints are required for joints bent more than 15 degrees. Under 15 degrees, universal, or Cardan joints, are able to maintain constant velocity for both the input and output shafts. Cardan joints resemble two U-shaped pieces offset from each other by 90 degrees and connected with a cross-shaped piece. At greater than 15 degrees, Cardan joints begin to create serious vibration problems at higher speeds.