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Pelican Technical Article:

Replacing the Upper Control Arm

Mike Holloway

Time:

2 hours2 hrs

Tab:

$250 to $1300

Talent:

**

Tools:

Floor jack, jack stands, wheel chocks, safety glasses, lug wrench, torque wrench, 19mm open-end wrench,

Applicable Models:

Mercedes-Benz R107 (1972-80)

Parts Required:

Control Arm Pelican Part #115-330-38-07-M36 Left (Bilstein), #115-330-39-07-M36 Right (Bilstein) or 115-330-38-07-M36 Left (OEM), 115-330-39-07-M36 Right (OEM), Control Arm Bushing Kit Front Lower Inner Pelican Part # 115-330-16-75-M36 (Bilstein) and Control Arm Bushing Kit Front Upper Inner Pelican Part # 115-330-17-75-M36 (Bilstein)

Hot Tip:

Slowly lower the lower control arm until all the pressure is off of the coil spring

Performance Gain:

Better handing, less vibration, smoother ride, and increased tire life

Complementary Modification:

Replace shock absorbers

There are many different types of suspension systems. There is the older double wishbone suspension, which uses two control arms -- one upper and one lower to keep the spindle in the correct position while the suspension moves through its travel. This is the preferred suspension system for sports cars, because the upper and lower control arms keep the wheel straighter throughout its suspension travel. This reduces the effect called bump steer. Bump steer is the change in the angle of the tire as the suspension compresses and expands. If the wheel changes its angle as the suspension is moved up and down the car is said to have a lot of bump steer. This changes the direction of a car as the outside suspension compresses under load in a turn. If bump steer is managed properly with suspension geometry it can actually improve the handling of a car. More often than not it leads to unnecessary steering adjustments while driving. The MacPherson strut is another type of suspension. In this suspension system there is no upper control arm. The upper spindle is mounted to the lower part of the strut and the strut controls the path of the spindle as the suspension moves. This usually increases camber (the angle of the tire relative to the road) but under hard cornering during spirited driving more camber is usually a good thing. Most MacPherson struts have the coil incorporated with the shock absorber. In either case each suspension system has a lower control arm. If the ball socket is worn out you will need to replace the whole lower control arm.

As you drive your car your front suspension needs to do two jobs. It needs to pivot left and right in the direction you want to turn. It also needs to move up and down with suspension movement. Bushings are not capable of this kind of flexibility. In rear suspensions you can use more bushings because there is no left to right steering movement. Ball joints are used to allow the steering angle to change with any up and down movement of the suspension. Mercedes-Benz uses two control arms, an upper and a lower to allow the spindle to move up and down with suspension movement and still allow the steering input to pivot the spindle. The lower ball joint is serviceable separately. The upper ball joint is built into the upper control arm. This means to service this component you need to replace the whole upper control arm. With all this left and right movement and up and down suspension movements these ball joints can wear out. When a ball joint wears out the spindle is allowed to move around while driving causing noises during suspension movement and also uneven tire wear.

In this tech article I will go over all the steps to remove the upper control arm with built in upper ball joint. These fasteners are going to be tight and there may not be a lot of room to swing the wrench. You are going to have to be patient and use some force to remove fasteners and components to rebuild your front end. Corrosion may hold a component in even after you have loosened a fastener. Keep in mind the joint may pop out when you use a removal tool so keep your hands clear and wear protective gloves. When this happens it will scare the heck out of you. I know this for a fact because it scared the heck out of me when it popped.

Lift and support the front axle of the vehicle. You have to remove the tires to perform this job, and it does make access much easier since you may not have access to an automotive lift. See our tech article on jacking and supporting your vehicle and removing the front tires. The procedure to replace the front upper ball joint is the same for both the left and right side. In these pictures we are working on the passenger side. Keep in mind all the steps apply to both sides. It is recommended you replace both sides at the same time to keep your handling neutral. Remember, the ball joint is attached to the upper control arm. You cannot change out the ball joint without replacing the upper control arm as well.

Remember that your car may have been serviced before and had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Before you do any work on your car it is important that you wear safety glasses and work gloves. If you have to jack up your car, make sure to use jack stands and chock your wheels as well as applying the parking brake. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. Never work on your vehicle if you feel the task is beyond your ability. Always disconnect the battery before working on your car.

Lift and support the front axle of the vehicle.
Figure 1

Lift and support the front axle of the vehicle. Place a jack stand under the lower control arm. You have to remove the tires to perform this job, which makes access much easier since you may not have the use of an automotive lift. See our tech article on jacking and supporting your vehicle and removing the front tires. 

I placed a jack stand under the chassis as well.
Figure 2

I placed a jack stand under the chassis as well. The procedure to replace the upper control arms is the same for both the left and right sides. These pictures are of the passenger side of the vehicle. It is recommended you replace both sides at the same time to keep your handling neutral. Placing a jack stand under the chassis provides additional safety.

The upper control arm is fixed to the frame as well as the steering knuckle (red arrow).
Figure 3

The upper control arm is fixed to the frame as well as the steering knuckle (red arrow).

Do not remove the shock absorber.
Figure 4

Do not remove the shock absorber. The first nut to remove is on the steering knuckle.

Using a 19mm open-end wrench, loosen and remove the nut from the ball joint.
Figure 5

Using a 19mm open-end wrench, loosen and remove the nut from the ball joint.

You may choose to remove the brake line.
Figure 6

You may choose to remove the brake line. I was able to remove the upper control arm without having to do this step but as long as you are there, you can look to bleed the lines of air if they feel squishy or you want to change brake fluid. 

Using a 14mm line wrench, loosen the brake line.
Figure 7

Using a 14mm line wrench, loosen the brake line. Make sure you have the proper receptacle to collect brake fluid if you decide to do this step. Again, it is optional and not required to carry out the removal and replacement of the upper control arm.

Using a separator tool, fix it to the ball joint and slowly turn the tools screw to begin to separate the ball joint from the steering knuckle.
Figure 8

Using a separator tool, fix it to the ball joint and slowly turn the tools screw to begin to separate the ball joint from the steering knuckle. Please keep in mind that there may be a 'pop!' when it gives way. It will scare the heck out of you but that will be the extent of it. 

After the ball joint is free, the upper control arm should be able to move up and down.
Figure 9

After the ball joint is free, the upper control arm should be able to move up and down. Move it back and forth in order to gauge the amount of play there is on the bushings. 

The upper control arm is secured to the frame with two 19mm bolts.
Figure 10

The upper control arm is secured to the frame with two 19mm bolts. 

Using a 19mm wrench and 19mm socket, loosen and remove each bolt.
Figure 11

Using a 19mm wrench and 19mm socket, loosen and remove each bolt. The upper control arm and ball joint are now free to be replaced. Installation is the reverse of removal. 


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