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Article > Chassis (Suspension/Steering)

Ball Joints Critical To Steering, Suspension


10/16/2013
By Larry Carley

On some of these unitized control arm applications, it is possible to replace the joint separately even though the control arm was not designed that way.
 
Ball joints are chassis components that eventually wear out and have to be replaced. But the ball joints on many late-model vehicles are now part of a unitized control arm assembly rather than a separate component. The car makes do this to save weight and cost (for them, not your customers!). So on many of these applications, your customer has to buy a complete control arm assembly rather than an individual ball joint if their vehicle needs a new ball joint.

On some of these unitized control arm applications, it is possible to replace the joint separately even though the control arm was not designed that way. Aftermarket chassis parts suppliers are very clever at coming up with ways to save your customers money, so if it’s possible to press a ball joint out of a unitized control arm they probably have a replacement joint that will fit. But if it is not possible to replace the joint, your customer will need a whole new control arm assembly.

On applications where the ball joints can be replaced, installation may require unbolting the joint, pressing out the joint or drilling out rivets that hold the old joint in place. The degree of difficulty can vary greatly from one application to the next, so some DIYers may not know what they’re getting into until they start to tear their car apart.

A classic symptom of worn ball joints is suspension noise when hitting bumps (clunks and rattles), and inner shoulder wear on the front tires due to camber misalignment. Ball joint wear can be checked by raising the wheels off the ground and using a small pry bar with light pressure only
to check for excessive movement in the joint or looseness. Some ball joints have built-in wear indicators that indicate wear when the wheels are on the ground.

Either way, it’s time to replace the joint if wear exceeds factory specifications.

On cars and trucks that have short long arm (SLA) suspensions, there are four ball joints: one upper and one lower on each side. The load bearing joint (which may be the upper or lower depending on where the spring is located) is the one that experiences the most wear.

On cars with MacPherson strut suspensions, there are no upper ball joints — unless it has a “wishbone” strut suspension with upper control arms, in which case there will be upper ball joints.

If one ball joint is worn out, chances are the ball joint on the opposite side is also bad or nearing the end of its service life. Many technicians recommend replacing both joints at the same time (both lowers, both uppers or all four).

Another item that should be checked when ball joints are replaced is the stud hole in the steering knuckle — especially if the ball joint stud has broken or is loose. An out-of-round hole can allow flexing that leads to metal fatigue and stud breakage. The new ball joint stud should fit snugly in the hole without rocking, and only the threads of the stud should extend above the hole.

On front-wheel drive suspensions that use a pinch bolt arrangement to lock the ball stud in the knuckle, the pinch bolts are often torque-to-yield and should not be reused but replaced with new bolts.

Other steering and suspension parts that may be worn out and in need of replacement include tie rod ends, control arm bushings, idler arms, steering rack bellows and rack mounts. These parts should also be inspected and replaced as needed when the ball joints are replaced.

Finally, wheel alignment should be checked and adjusted to specifications as needed following the installation of new ball joints or unitized control arm assembles. If the wheels are not aligned, tire wear, steering and handling may all be affected.












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