How to Detect a Bad U Jointby Christian Killian
Universal joints are a critical component of the drive line in your car. Understanding how to recognize a worn universal joint before it fails will save you from having to replace more expensive parts. When a universal joint fails, it can damage the drive shaft, the yoke on the differential, and the yoke, tail shaft, and output shaft of the transmission itself. Routine maintenance and lubrication of the universal joints can greatly extend the life of the joint and save you the time of having to replace parts more often than necessary.
Listen carefully to the vehicle as it is moving, and take note of any squeaking or metallic sounds coming from under the vehicle. These sounds can indicate a universal joint that has dried out or is under-lubricated.
Take note of any vibration in the vehicle caused by a worn drive shaft universal joint. These vibrations typically appear when the joint is close to failure. If you detect a vibration, do not dismiss it.
Stop the vehicle in a safe spot such as a driveway or parking lot. With the engine running and your foot on the brake, shift the car from park into reverse and listen for a clunking or banging noise as it goes into gear. You will often feel it jump when it bangs, indicating a loose universal joint.
Park the car on flat ground and shut the engine off. With the car in park and the wheels chocked for safety, try moving the drive shaft by turning it and note any play in the universal joints of the shaft. Loose joints can allow the shaft to move as much as a quarter-inch to a half-inch in either direction when turned.
Insert a large, flat screwdriver into the yoke that connects the drive shaft to the transmission yoke or differential yoke. Try turning the shaft by pushing up or pulling down on the screwdriver. Note any movement in the shaft that would indicate a loose joint.
Inspect the universal joints using a flashlight. Look into the yokes for chipped or broken bearing caps, rust or missing bearings and retaining clips. These signs are indications of a severely worn universal joint.
- Universal joints should be routinely greased and inspected for signs of wear. Replace factory universal joints with high-quality aftermarket joints to get longer service from the joint.
- A damaged or worn universal joint can fail and cause severe or even catastrophic damage to the vehicle.
- Vibration of the drive shaft caused by a worn universal joint can cause damage to the bearings on the output shaft of the transmission if left unchecked.