Chassis parts are usually sold when a customer realizes his vehicle has a tire wear, handling, steering, alignment or suspension problem. Worn chassis parts such as ball joints and control arm bushings can change camber alignment, causing shoulder wear on tires. Worn tie rod ends in the steering linkage can allow toe alignment to change, causing tires to wear rapidly. A worn idler arm in a vehicle that does not have rack and pinion steering can make the steering feel loose and the vehicle to wander on the highway. Even relatively simple parts such as sway bar bushings and links can cause problems, too, such as squeaking and rattling if they are worn, cracked or loose.
Ball joints connect the control arms to the steering knuckles. The original equipment ball joints on most late-model vehicles are sealed and require no maintenance (grease), but that doesn’t mean they last forever. The relentless pounding that occurs with every bump in the road eventually produces wear and looseness between the ball stud and its support bushing inside the ball joint. Load-bearing ball joints typically experience the most wear.
Ball joints with lots of wear are dangerous and should be replaced because there is a danger the joint may break or pull apart, allowing the suspension to collapse. Some play is acceptable, but if play exceeds specifications (which will vary depending on the application), it’s time to replace the joints. On high-mileage vehicles, replacing all of the joints at the same time is recommended if one or more joints are worn beyond specifications.
On some vehicles, the ball joints are part of a “unitized” control arm assembly. On most of these applications, the entire control arm assembly must be replaced with a “loaded” control arm if the ball joint is worn out unless the arm has a press-fit joint that can be removed and replaced with an aftermarket ball joint. Loaded control arms come with new joints and bushings, and are ready to install, which saves installation time compared to drilling or pressing out an worn ball joint.
Another replacement option for some vehicles is to replace the original equipment style sealed ball joint with a greasable joint that has a metal gusher style bushing. These may be required on pickup trucks that are subject to hard use or off-road driving.
Tie rod ends usually need to be replaced when there is any visible play in the joint. As with ball joints, when one tie rod end is worn out, the other(s) are likely nearing the end of their service life, too. Replacing all at the same time is usually recommended on high-mileage vehicles. The same advice goes for the inner tie rod sockets on vehicles with rack and pinion steering. Left and right tie rod ends are usually threaded differently (right and left hand threads), so if a customer is only replacing one end make sure it is for the correct side.