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Rear Lower Control Arm Replacement
 
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Pelican Technical Article:

Rear Lower Control Arm Replacement

Kerry Jonsson

Time:

6 hours6 hrs

Tab:

$400

Talent:

***

Tools:

12mm twelve point socket bit, 12mm Allen head socket, 13mm, 18mm, 21mm wrench and or socket with ratchet

Applicable Models:

Mercedes-Benz W211 (2003-09)

Parts Required:

Rear lower control arm

Hot Tip:

Spray the fasteners with penetrating oil before removing

Performance Gain:

Improve handling and correct uneven tire wear

Complementary Modification:

Replace the rear rearward lower link if necessary

Mercedes Benz uses a multiple link rear suspension system on their W211 chassis. These multiple links hold the spindle in proper alignment to the road while the suspension moves through its travel. These links are smaller and are not designed to carry the weight of the car. The lower control arm is the one large suspension component that suspends the weight of the car. The rear coil spring is mounted in between the lower control arm and the spring perch on the body. Although it is essentially a metal arm there is a rubber bushing built into the lower control arm spindle mount. This rubber bushing allows for flexibility as the suspension moves up and down. Over time this rubber bushing can dry out and crack from exposure and road salts used to clear roads. If the lower control arm rubber bushing wears out it will allow the lower part of the spindle to move around in corners and result in unusual handling characteristics. A second symptom would be uneven tire wear. Typically the inside tread of your tire would wear out faster due to the excessive camber from a worn lower control arm bushing.

Lift and support the rear axle of the vehicle. Before you do any work under your vehicle, make sure you're wearing safety glasses. You don't want to get any rust particles in your eyes. 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 rear tires.

The procedure to replace the rear lower control arm is the same for both the left and right side. In these pictures we are working on the right 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 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

This picture illustrates the rear of the right side rear wheel well.
Figure 1

This picture illustrates the rear of the right side rear wheel well. Remove the rear rearward lower link to spindle mount fastener using a 10mm Allen head socket on one side of the fastener and an 18mm wrench on the other side to hold it still. You do not have to remove the brake caliper and rotor to do this job. We have done so to provide you with a better view of the work.

Remove the rear rearward lower link outer mount fastener from the spindle by moving it in the direction of the blue arrow.
Figure 2

Remove the rear rearward lower link outer mount fastener from the spindle by moving it in the direction of the blue arrow.

This picture Illustrates under the by the right side lower control arm mount to the sub frame.
Figure 3

This picture Illustrates under the by the right side lower control arm mount to the sub frame. Remove the T55 Torx fastener (green arrow). If you want, you can remove the 18mm fastener (red arrow). It is a tight fit.

Use a T55 Torx socket to remove the toe adjustment fastener.
Figure 4

Use a T55 Torx socket to remove the toe adjustment fastener.

Pull the arm down away from the car.
Figure 5

Pull the arm down away from the car. Be careful not to lose or damage the toe adjustment shim of the rear lower link sub frame mounting bracket (green arrow).

This picture illustrates looking up under the right rear lower control arm.
Figure 6

This picture illustrates looking up under the right rear lower control arm. Remove the plastic rivets (green arrows).

To remove the plastic rivet pull the center pin (green arrow) into the direction of the blue arrow, then you can pull out the entire plastic rivet.
Figure 7

To remove the plastic rivet pull the center pin (green arrow) into the direction of the blue arrow, then you can pull out the entire plastic rivet.

Pull the lower control arm plastic cover off the lower control arm.
Figure 8

Pull the lower control arm plastic cover off the lower control arm.

Next you have to remove the three fasteners (green arrows), see the following steps.
Figure 9

Next you have to remove the three fasteners (green arrows), see the following steps.

Using a 12mm triple square socket on a breaker bar and an 18mm wrench, remove the inner lower control arm mount fastener but leave the bolt in the arm.
Figure 10

Using a 12mm triple square socket on a breaker bar and an 18mm wrench, remove the inner lower control arm mount fastener but leave the bolt in the arm.

Using a T50 Torx socket with breaker bar and 13mm wrench remove the lower shock absorber fastener.
Figure 11

Using a T50 Torx socket with breaker bar and 13mm wrench remove the lower shock absorber fastener. You will not be able to pull the bolt out of the lower control arm yet.

This picture illustrates the rear view of the lower control arm spindle mount.
Figure 12

This picture illustrates the rear view of the lower control arm spindle mount. Using a 21mm socket remove the fastener.

Using a 12mm Allen head socket hold the fastener still while you remove the other side.
Figure 13

Using a 12mm Allen head socket hold the fastener still while you remove the other side.

Using two breaker bars remove the fasteners.
Figure 14

Using two breaker bars remove the fasteners. This fastener is going to be very tight since it is a load bearing member.

Before removing any fasteners support the lower control arm with a jack.
Figure 15

Before removing any fasteners support the lower control arm with a jack. You may even have to jack up the lower control arm a little to take the load off of the fasteners. Now you can remove the three fasteners you just loosened.

Slowly and very carefully lower the jack until you have taken all the tension out of the spring.
Figure 16

Slowly and very carefully lower the jack until you have taken all the tension out of the spring. Make sure youÂ're wearing your safety glasses. Move the lower control arm in the direction of the blue arrow to remove the lower control arm from the spindle. You can use a pry bar and lever it out or tap it with a mallet to drive it out of the spindle mount.

Remove the parking brake cable from its mount in the lower control arm.
Figure 17

Remove the parking brake cable from its mount in the lower control arm. There is normally a plastic bushing in the mount but the one on our car is missing. The bushing pulls straight out.

Remove the lower control arm from the car.
Figure 18

Remove the lower control arm from the car. Installation is the reverse of the removal steps. Install the lower control arm in the spindle and line up the mounts to install the fastener. Fit the spring and jack up the lower control arm until you can install the shock absorber lower mounting fastener and the lower control arm to sub frame mounting fastener. Install the lower control arm plastic cover and plastic rivets. Install the rear rearward lower link and tighten the fasteners. Fit the wheel and take the car for a four wheel alignment.

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