A U-joint, which is the shortened term for Universal joint, is a joint composed of two "U" shaped ends connected together by an "X" shaped coupler. The drive shaft on a vehicle is composed of two U-joints, one on the front and one on the back. A U-joint that is going out cannot be identified visually. Recognizing the symptoms of a U-joint that's going bad is imperative for safety. The drive shaft of a vehicle may collapse if the worn U-joint breaks. The car may be propelled into the air if the drive shaft collapses while the vehicle is in motion.
A U-joint that is worn down may cause a clunking noise. A worn U-joint may also cause a rumbling or rattling sound, and may cause the floorboards or the gear shift to vibrate.
A squealing sound at low-speeds may indicate that one of the U-joints are going out. The squealing sound may disappear at highway speeds and reappear as the car slows during stops.
Drive shaft play, which is any movement of the drive shaft when manually tugged on, is a strong indication that one or both U-joints are going out. Raise the car on a hydraulic lift so that the tires hang freely. Try to move the drive shaft from side to side to test the U-joints. Have the U-joints replaced if the drive shaft moves at all.
