Ball joints are the critical component of the front suspension that connect various links and allow them to move. Ball joints consist of a ball and socket similar to the hip joint of the human body. Ball joints of your front suspension provide pivoting movement between the steering knuckles and control arms to provide a safe, smooth ride and allow you to precisely control your vehicle.
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Ball joints consist of a metal housing and a stud that can swing and rotate within the housing. Bearings inside the housing are placed between the ball stud and housing to help reduce wear and friction. The socket is filled with grease to provide lubrication, keep debris and water out of the socket, and maintain noise free operation. A rubber boot, located at the opening of the joint, keeps debris out and grease in. Lastly, the assembly is closed with a method such as the MOOG® pressed-in cover plate.
Many original equipment ball joints are designed as sealed units. If the protective boot fails, water and road debris will quickly cause wear and ball joint failure. Some aftermarket ball joints use an improved greaseable design that allows lubrication to flush out contaminants to extend the life of the joints.
In your vehicle, you’ll find two different types of ball joints – upper ball joints and lower ball joints. While each of these ball joints serve different functions but both work together to keep steering reliable and responsive.
Designed to maintain alignment and absorb radial loads, such as turning forces, upper ball joints enable proper rotation of steering knuckle. Upper ball joints use a follower design.
Acting as a pivot point for the steering system, lower ball joints can either be load-carrying or follower types depending on the suspension design. Lower ball joints use a variety of designs: compression loaded, tension loaded and follower.
In a short long arm (SLA) suspension system, compression- and tension-loaded ball joints are load carrying ball joints that support the vehicle’s weight. These ball joints typically wear faster due to the additional stress on the socket. In MacPherson strut suspension systems, the lower ball joint is a follower design. Although they do not support the weight of the vehicle, they receive loading during cornering and braking.
When you need to replace a ball joint, MOOG has a ball joint for the repair. MOOG ball joints include technologies to increase strength and durability, extend service life and improve ease of installation. They restore like-new steering with application-specific features such as patented pressed-in cover plate and integral dust boot, instilling confidence with each install.
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The content in this article is for informational purposes only. You should consult with a certified technician or mechanic if you have questions relating to any of the topics covered herein. Tenneco will not be liable for any loss or damage caused by your reliance on any content.
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.
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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.
Contact us to discuss your requirements of ball joint manufacturer. Our experienced sales team can help you identify the options that best suit your needs.