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Rear Forward Lower Link Removal and Replacement
 
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Pelican Technical Article:

Rear Forward Lower Link Removal and Replacement

Kerry Jonsson

Time:

5 hours5 hrs

Tab:

$200

Talent:

***

Tools:

13mm, 17mm, 19mm wrenches and/or sockets with ratchet

Applicable Models:

Mercedes-Benz R129 (1990-02)

Parts Required:

Rear lower control arm

Hot Tip:

Spray the fasteners with penetrating oil before removing

Performance Gain:

Improve handling and uneven tire wear

Complementary Modification:

Replace the rear shock absorbers if necessary

The W129 chassis uses a multiple link suspension system in the rear of the car. The advantage of having a multiple link suspension is the angle of the spindle to the road can be controlled as the components move through their suspension travel. Keeping the angle of the spindle consistent throughout suspension travel gives the driver neutral handling no matter how hard the driver wants to turn into a corner. The suspension links do hold the spindle in the correct position but they do not carry the weight of the car. The rear lower control arm carries the weight of the car. The rear coil spring is mounted in between the lower control arm and the spring perch on the sub frame. The lower control arm is an arm but it does have a rubber bushing on the sub frame mount side of the arm. This rubber bushing can wear out over time. The rubber dries up and cracks form in the rubber insert. This allows the lower control arm to move around as the suspension moves up and down. This can cause unusual handling characteristics and uneven tire wear. Typically the inside treads of the tire wears out prematurely with the excessive camber caused by a worn lower control arm bushing. In this tech article I will go over the steps to replace your rear lower control arm.

Lift and support the rear axle of the vehicle while wearing your safety glasses. 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 rear lower control arm is the same for both the left and right side. In these pictures I am working on the left 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 I give may be different from what you have so be prepared with different size sockets and wrenches

ThisPicture illustrates underneath the left side of the subframe.
Figure 1

ThisPicture illustrates underneath the left side of the subframe. Locate the hydraulic roll bar sensor (green arrow).

Unplug the electrical connection to the hydraulic roll bar sensor (green arrow).
Figure 2

Unplug the electrical connection to the hydraulic roll bar sensor (green arrow).

Push the metal locking tab in to unlock the electrical connector.
Figure 3

Push the metal locking tab in to unlock the electrical connector.

Unplug the electrical connector from the hydraulic roll bar sensor.
Figure 4

Unplug the electrical connector from the hydraulic roll bar sensor. Remove the 10mm fastener (green arrow).

Remove the hydraulic roll bar sensor from the car.
Figure 5

Remove the hydraulic roll bar sensor from the car.

Remove the brake pad wear sensor harness from the lower control arm mount.
Figure 6

Remove the brake pad wear sensor harness from the lower control arm mount. You do not have to remove the brake caliper and brake rotor to do this job. I have done so to enable you to see the work that is taking place.

Remove the brake pad wear sensor harness from the second mount.
Figure 7

Remove the brake pad wear sensor harness from the second mount.

Remove the 10mm plastic cover fastener.
Figure 8

Remove the 10mm plastic cover fastener.

ThisPicture illustrates looking up at the lower control arm from underneath.
Figure 9

ThisPicture illustrates looking up at the lower control arm from underneath. Remove the 10mm fastener (green arrow).

Remove the lower plastic cover from the lower control arm.
Figure 10

Remove the lower plastic cover from the lower control arm.

Using a 19mm socket with ratchet and wrench, remove the lower control arm fastener.
Figure 11

Using a 19mm socket with ratchet and wrench, remove the lower control arm fastener. Do not remove the fastener from the mount yet. Place a hydraulic jack under the lower control arm.

Remove the 13mm fastener for the rear sway bar link lower mount.
Figure 12

Remove the 13mm fastener for the rear sway bar link lower mount.

Remove the 16mm fastener for the shock absorber lower mount.
Figure 13

Remove the 16mm fastener for the shock absorber lower mount.

Remove the 22mm fastener for the lower control arm to spindle mount.
Figure 14

Remove the 22mm fastener for the lower control arm to spindle mount.

With the hydraulic jack supporting the lower control arm, remove the four fasteners you just loosened.
Figure 15

With the hydraulic jack supporting the lower control arm, remove the four fasteners you just loosened.

Slowly lower the jack until all of the tension on the coil spring is relieved.
Figure 16

Slowly lower the jack until all of the tension on the coil spring is relieved. Be well away from the suspension and the floor jack's arm. Also, you better be wearing those safety glasses.

Remove the lower control arm from the car.
Figure 17

Remove the lower control arm from the car. Installation is the reverse of the removal steps. Fit the lower control arm into the sub frame mount and install the fasteners but do not tighten them yet. Use the jack to jack up on the lower control arm and compress the coil spring. Do this to line up the holes for the rear spindle, rear lower shock absorber and rear sway bar link mounts. Install the lower control arm to spindle mount, rear sway bar link mount and rear shock absorber mount. Once all of the fasteners are installed, tighten the fasteners. Install the brake pad wear sensor wiring harness in the holder of the lower control arm and install the lower plastic cover and fasteners. Install the hydraulic roll bar sensor and plug it in. Fit the wheel, lower the car and you are done.

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