Whats the difference between a U-joint and a constant velocity (CV) joint?
A U-joint (the “U” stands for “Universal”), which is also called a “Cardan” joint after the guy who invented it, is a type of flexible coupling typically used on both ends of the driveshafts in rear-wheel and four-wheel drive vehicles. Each U-joint consists of a four-legged center cross with needle bearing cups on the ends of each leg of the cross. The bearing cups on one pair of legs are mounted to the driveshaft. The other pair of cups are held in place by a pair of U-bolts attached to a yoke that mates to either the transmission or differential. The bearing cups allow the joint to swivel and bend as the driveshaft follows the motions of the differential and axle as the suspension bounces up and down. Most original equipment U-joints on newer vehicles are “sealed” and do not require periodic greasing. But many replacement U-joints as well as the U-joints on older vehicles do have a grease fitting which allows the joint to be lubed periodically. CV Joints: Aconstant velocity (CV) join
