- In some vehicles it is recommended that you check to see if the grease fitting can wiggle in the ball joint. If it does, the ball joint should be replaced. Always check the service manual when checking ball joints.
- Some ball joints have a wear indicator built into them. The most common type of wear indicator has a shoulder that sticks out of the bottom of the joint about 0.050" when it is new. If the ball joint has worn, this shoulder will recede into the ball joint housing. When it is flush, the ball joint should be replaced. A wear indicator ball joint must be loaded and at normal ride height to read the indicator.
Checking a wear indicator ball joint. Courtesy of Moog Automotive, Inc.
- Ball joints should be checked for excessive wear and torn grease seals. Look for unusual tire wear. Worn ball joints or other front suspension parts that cause looseness can result in cupped wear of the tire tread. A torn or missing ball joint seal will require replacement of the joint by a front suspension specialist. Bad shock absorbers or a tire out of balance can also result in cupped wear.
- Feel around the outside of the boot, looking for tears. If the boot is torn, the joint will probably fail soon and should be replaced.
- Inspect also for signs of rust or cracks on the control arm near the joint.
- Load carrying joints will have some slop when the weight of the vehicle is taken off them. Follower joints should never have play.
- To check a load-carrying joint, it must be unloaded. When the coil spring is on the lower control arm, raise the vehicle by jacking under the control arm as close to the ball joint as possible. This gives the maximum amount of leverage against the spring.
- The ball joint is unloaded when the upper strike out bumper is not in contact with the control arm or frame. A quick check for looseness can be made by using a pry bar between the tire and the ground.