Universal joint (U-joint)

A universal joint, U-joint or cardan joint, connects two shafts that meet at an angle and lets rotation pass between them. The common type has two yokes linked by a cross-shaped spider with needle bearings.

On shaft-drive motorcycles, the joint sits at the gearbox end of the drive shaft so the shaft can follow the swingarm's up-and-down movement. ATVs and UTVs use universal joints and CV joints in their propshafts and drive axles.

Signs of wear include a clunk when changing between throttle on and off, play when you rock the rear wheel, or vibration. Some joints have grease nipples and should be greased at service intervals; sealed types are replaced when worn. After riding through deep water, check the joints and boots.