Although not a common repair, there are times when it is necessary to replace a car's control arm. This is an important structural part of the vehicle's front suspension, attaching the wheel hub and steering knuckle assembly to the vehicle's frame.
Many vehicles can go through their entire life without ever having a control arm replaced. However, some situations necessitate the control arm's replacement. There are three basic reasons why a control arm might need to be replaced:
Cause of Control Arm Failure
Vehicle is in a front-end accident or one where the front wheel becomes damaged, causing a bent control arm; control arm either rubs against the wheel well all the time or when turning
Worn ball joint
Ball joint may be permanently pressed into control arm, making it impossible to replace the ball joint without replacing the control arm; steering is sloppy, producing a thumping noise; occurs primarily with later-model cars
Bushings where the control arm is attached to the frame are necessary to allow the wheel to move up and down as it travels across bumps and dips in the road; if bushings become excessively worn, the vehicle produces a thumping or rattling noise; control arm must be removed to replace bushings
If your car displays any of the above symptoms, the control arm may need to be replaced. If this is the case, please proceed with the troubleshooting and control arm replacement instructions described in this guide.
Checking the Control Arm
If a control arm is suspected of being bad, it can be checked without removing it from the vehicle. To do so, jack up the suspect wheel and move it back and forth, up and down, and in and out, looking for play in the ball joint, the bushings, and other suspension and steering components. Please note that thumping sounds and sloppy steering can be caused by a number of suspension and steering components. It is necessary to identify the component that is moving in a way that is should not.
When ball joints are worn, they allow the wheel hub to move in and out from the vehicle when adjusted by hand. The movement at the ball joint should be visible, as the relation of the steering knuckle to the arm will change, showing the slop in the ball joint. On vehicles that do not have McPherson struts, there will be an upper control arm as well, with another ball joint. Be sure to check both.
If the control arm bushings are worn, they will allow the control arm to move out and away from the vehicle's frame when the wheel hub is moved in and out. This may be a very small movement, but there should be no movement at all.
While checking, also look at the steering tie rod end, where it attaches to the steering knuckle. Just like the ball joint, there should be no side-to-side movement. Wear in the tie rod end can cause problems with steering, although it will not create any thumping sounds.
The sway bar also connects to the control arm, but this is mounted with a stud and bushing arrangement that is intended to allow flexibility. The sway bar deals with upward and downward movement, so any movement in it is immaterial.
Car Front-End Anatomy
The front end of a car has many parts, which can be confusing to those who are not used to working on them. Three different systems are in place, all of which have to work together and pass through one another. These are the suspension system, the steering system, and the drivetrain system.
The steering system does just what it sounds like it does: helps the driver steer the vehicle. When looking at the front of a vehicle with the wheel removed, the only part that is easily visible is the tie rod. This will connect to an arm sticking out from the steering knuckle and wheel hub. The connection is through a small ball joint. This connection should not be removed while replacing the control joint. If it is removed, it must be replaced in exactly the same position, or the vehicle alignment will be off.
The drivetrain consists of the engine, transmission, and drive shafts. On a rear-wheel drive vehicle, this is not visible from the front wheels. On a front-wheel drive vehicle, the driveshaft goes from the transmission to the front wheel hub. In the midst of it, there is a constant velocity joint (CV joint) that allows it to be flexible. Check the rubber boot over this joint to ensure that it is not turned.
Everything else that is visible in the front wheel area is part of the vehicle suspension. The most visible part is the wheel hub and steering knuckle assembly, which is what the wheel was mounted to. The control arm is attached to the bottom of this assembly, which goes back to the vehicle frame. On vehicles that have McPherson struts, the struts are attached to the upper part of the wheel hub and go up to the top of the engine compartment. On vehicles with shocks and springs, there is a second control arm, which is attached to the top of the wheel hub and the vehicle's structure. The last important component is the sway bar, which crosses the vehicle, connecting one control arm to the other.
Preparing the Vehicle for Removing the Control Arm
Replacing the control arm requires getting under the vehicle. Therefore, it is extremely important that the vehicle is properly raised and supported. Failure to properly support the vehicle can allow it to fall while working under it.
The vehicle must be on a flat surface (not on an incline) that is hard enough to support a jack and jack stand without them sinking into the surface. A concrete driveway is best. If the work is being done over dirt, the dirt needs to be dry and well compacted so that the jack stands cannot sink into it. A 1-foot square piece of plywood under the jack stands can help prevent any sinking.
Break loose the wheel lug nuts before jacking up the vehicle, but do not remove them. Block the rear wheels before jacking. This can be done with a stone, a scrap piece of dimensional lumber, or wheel chocks. The block or chock should be placed tightly behind the wheel so that the car cannot roll backward.
Using a floor jack or scissors jack, raise the vehicle high enough to allow working under it. Be sure to locate the jack on a frame member, or in the case of a car with a unibody construction, at a jacking point where there are several thicknesses of metal together to support the jack. Most modern cars have reinforced jacking points located right behind the front wheel wells for this purpose.
With the vehicle raised, the lug nuts can be removed and the wheel taken off. Place a jack stand under the vehicle, at a point where the frame or unibody construction is sufficiently strong to support the weight of the vehicle. Most cars, even those with unibody construction, have a structural member for the control arm to connect to. This is an excellent location for a jack stand, as long as the stand can be placed in such a way as to not interfere with removing the control arm.
Please note that it is not safe to work under a vehicle that is only supported by a jack. Hydraulic floor jacks bleed off their pressure through time, slowly dropping the vehicle. Scissor jacks and bottle jacks are unstable. If the car is bumped or tries to roll slightly, it can fall off these types of jacks.
Removing the Control Arm
With the vehicle raised and properly supported, and the wheel removed, it is possible to access the control arm and any other front suspension parts. Start by disconnecting the bushing that attaches the sway bar to the control arm. The sway bar can stay in place; it only needs to be disconnected from the control arm.
If the vehicle has two control arms, an upper and a lower, the suspension spring is mounted between them. The lower control arm must be supported with a floor jack before anything else is removed.
Disconnect the lower ball joint (which is attached to the control arm) from the wheel hub and steering knuckle. To do so, the castle nut on the end of the ball joint must first be removed. There is a cotter pin through this nut to keep it from loosening. Remove and discard the cotter pin; a new one should be used on reassembly. Some cars use a pinch clamp to hold the ball joint to the wheel hub instead of a nut on the end of the ball joint stud; if this is the case, loosen the pinch bolt.
The ball joint needs to be removed from the steering knuckle with a ball joint separator or ball joint press. If space allows and the ball joint is going to be reused, a ball joint press is better, as it will not damage the rubber boot on the ball joint. If saving the ball joint is not a consideration, a ball joint separator is much faster and easier to use.
A ball joint separator looks like a large fork. The prongs of the fork are placed around the ball joint stud, between the steering knuckle and the control arm. The end of the separator is struck with a hammer, driving the prongs between the two parts. This causes them to separate. Most of the time, the rubber boot over the ball joint is ripped in this process. If the ball joint is to be reused, a new rubber boot should be installed.
Remove the control arm mounting bolts at the vehicle frame. The control arm can now be removed.
Installing the New Control Arm
The new control arm is installed exactly the opposite of how the old one was removed. If the purpose of removing the control arm is only to replace the bushings, the same control arm can be used, with new bushings in place of the old ones.
Start by locating the control arm under the vehicle and attaching it with the mounting bolts. Be sure to put the bushings in place at the mounting holes if they are not pressed into the control arm. Do not tighten the mounting bolts until all bolts are installed, including the ball joint stud.
Place the ball joint into the steering knuckle. On some vehicles, where the sway bar is under the control arm, it may be necessary to pry down on the control arm to align the ball joint stud with the steering knuckle. On vehicles that have upper and lower control arms, the lower control arm needs to be lifted into place with a floor jack, compressing the suspension spring. Attach the castle nut, but do not tighten.
Connect the sway bar to the control arm.
Torque the ball joint castle nut to manufacturer's specifications. Place a new cotter pin through the castle nut and the ball joint stud. It may be necessary to turn the castle nut from the fully torqued position to install the cotter pin; this is acceptable. Bend the ends of the cotter pin in opposite directions so that it cannot be removed.
Torque the control arm mounting bolts and sway bar to the manufacturer's specifications.
Reinstall the wheel and tire, mounting it with the same lug nuts that were removed. Lower the vehicle to the ground and retighten the lug nuts to ensure that they are fully tightened.
Buying Control Arms
Each vehicle model has its own specific control arm design. The right-hand and left-hand control arms are essentially mirror-images of each other. When buying a replacement control arm, it is important to specify the vehicle's model and whether a right or left control arm is needed. Often, the same control arm will fit all years for that car model.
Buying Control Arms on eBay Motors
Many different types of control arms for cars can be purchased on eBay Motors. Within the control arm category, there is a search box, allowing you to identify your vehicle's make, model, and year so that you can search for only those parts that fit the vehicle in question. If you have purchased parts for that vehicle on eBay Motors before, your vehicle identification information will be saved on the site, allowing you to select the vehicle from a drop-down list. Once your vehicle's information is entered or selected, you will see various listings for control arms that fit this vehicle. Then use the "Placement on Vehicle" category to narrow the listings to either right-side or left-side control arms.
Another easy way to search for a control arm on eBay Motors is to use the search bar that is located at the top of all eBay Motors pages. Simply type in the vehicle's year and model, which side you need, and the words "control arm," and eBay's search engine finds the parts you need. For example, a search for a "2000 Taurus RH control arm" delivers listings for new and used right-side control arms that fit a 2000 Ford Taurus.
Control arms may need to be replaced because of certain specific situations. If the vehicle has been in a front-end accident, there is a fairly high probability that the control arm needs to be replaced. It may also need to be replaced if the ball joint is bad and is pressed into the control arm. These types of ball joints are not replaceable without replacing the entire control arm.
While this may seem to be a daunting project, it actually is not all that difficult. A good breaker bar may be needed to loosen the bolts, and a torque wrench is needed to properly tighten everything when done. However, the job of replacing control arms is fairly easy.
The control arm is held in place at three points: the mounting bolts that hold it to the frame, the sway bar, and the ball joint that attaches to the wheel hub and steering knuckle. Once removed, the control arm comes right out. When installing the new control arm, be sure to install all fasteners before fully tightening them, as tightening the first one may make it harder to properly align the other fasteners in their holes.