Like brake pads and tires, chassis parts wear with every mile that’s driven. The rougher the roads, the greater the pounding these parts take. Rain and road salt also can contribute to the early demise of ball joints, control arm bushings, tie rod ends and other steering linkage components.
The main problems caused by worn chassis parts are things like road noise, steering looseness, road wander or pulling, wheel misalignment and accelerated tire wear. Worn chassis parts are usually discovered when a vehicle is aligned or when its tires are being replaced.
Most ball joints that mate the control arms to the steering knuckle on late-model vehicles are sealed for life and do not require any lubrication. Some replacement ball joints do have grease fittings, and may be recommended for hard-use applications like trucks. If play in a ball joint exceeds specifications, it needs to be replaced. Worn ball joints should not be ignored because if a ball joint pulls apart when it fails, the suspension will collapse and the driver may lose steering control.
As a rule, load-carrying ball joints wear out before non-load carrying joints. Ball joints are usually replaced in pairs (both lowers, both uppers or all four on vehicles that have SLA suspensions). Rear ball joints on independent suspensions wear, too, and should also be replaced in pairs.
On some applications, the ball joint is an integral part of a “unitized” control arm assembly so the entire control arm must be replaced if the ball joint is bad. On most other applications, the ball joint can be replaced separately. It may be bolted, riveted or pressed in place. A faster replacement alternative is to sell your customer a “loaded” control arm assembly that comes preassembled with a new ball joint and bushings and is ready to install. It saves installation time and reduces the risk of installer error.
Many ball joints are secured with Torque-To-Yield (TTY) bolts. These are essentially one-use fasteners because they stretch when they are tightened. If reused, there is a risk of breakage. New bolts are recommended for these applications.
Worn tie rod ends will affect tire wear more than anything else. Like ball joints, the tie rod ends need to be replaced if play exceeds specifications. Tie rod ends should also be replaced in pairs (both outers or the inner tie rod sockets with rack & pinion steering, or both outers or inners with recirculating ball steering). New tie rods or tie rod sleeves also may be required. The wheels must be realigned after the new tie rods have been installed.