How to repair universal joints fix

How to check them

If a rear-drive car clunks on acceleration or if a vibration occurs only at certain throttle positions, check the uni- versal joints (U joints) on the propeller shaft. Most shafts have a joint at each end; some have a double U-joint at one end. Many four-wheel-drive vehicles have two propeller shafts.

With the engine off and the transmission in neutral, raise the car at the rear, the front, or both. U s ing both hands, grab the shaft each side of a U-joint and try to twist the parts in opposite directions. If you feel any free play at all, have the joint replaced. Check all U-joints this way.

When looking for the cause of vibration, check the bolts holding the rear joint together. If you find any loose ones, tighten them. On a front-drive car, a humming sound indicates a problem with a universal joint on the axle shaft. Have a mechanic check it immediately.