Upper Control Arm - Rear

This procedure covers the removal and replacement of the rear upper control arm on a 2007-2013 Mercedes-Benz S65 AMG with the 6.0L V12 BiTurbo M275 engine.

Warnings

Tools required

Parts

• Rear upper control arm assembly × 1 — Use OEM specification
• Ball joint nut (if damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Chock front wheels to prevent rolling
3. Loosen rear wheel lug nuts while vehicle is on ground (do not remove)
4. Raise rear of vehicle and support on jack stands positioned at manufacturer-specified jacking points on chassis
5. Remove rear wheel on side being serviced
6. Spray all fasteners with penetrating oil and allow to soak for 10-15 minutes

Procedure

1. 1

   Support the rear knuckle assembly
   Position a floor jack with a block of wood under the rear knuckle/hub assembly to support it and prevent the suspension from dropping when the upper control arm is disconnected. Raise jack just enough to take light pressure off the upper control arm.
2. 2

   Remove ball joint nut
   Locate the upper control arm ball joint connection at the top of the rear knuckle. Remove the ball joint nut using an 18mm socket. Keep nut if reusable, otherwise discard.
   Torque spec

   Ball Joint Nut119 Nm (88 lb-ft)
3. 3

   Separate ball joint from knuckle
   Use a ball joint separator or pickle fork to separate the upper control arm ball joint stud from the knuckle. Insert the tool between the control arm and knuckle, then strike with a hammer or use the threaded separator tool to apply pressure until the taper releases. The separation may be sudden, so ensure the jack is supporting the knuckle.
   ⚠Ball joint may separate suddenly causing the knuckle to drop. Ensure jack is properly supporting the assembly.
4. 4

   Remove forward control arm mounting bolt
   Locate the forward mounting bolt that secures the control arm to the subframe/chassis. Use a 16mm socket to remove this bolt completely. Note the orientation of any washers or spacers for reinstallation.
   Torque spec

   Control Arm Bolts165 Nm (122 lb-ft)
5. 5

   Remove rear control arm mounting bolt
   Remove the rear mounting bolt that secures the control arm to the subframe/chassis using a 16mm socket. Support the control arm as you remove the last bolt to prevent it from falling.
   Torque spec

   Control Arm Bolts165 Nm (122 lb-ft)
6. 6

   Remove upper control arm
   Carefully maneuver the upper control arm out of the mounting location. It may require slight rotation or angling to clear surrounding components. Inspect the mounting points on the subframe and clean with a wire brush if necessary.
7. 7

   Prepare new control arm
   Compare the new upper control arm to the old unit to verify correct part. Check that all bushings are properly seated and that the ball joint dust boot is intact and not damaged.
8. 8

   Install new control arm loosely
   Position the new upper control arm into the mounting location on the subframe. Install both mounting bolts finger-tight only. Do not torque at this time as these bolts must be torqued with vehicle weight on wheels. Ensure any washers or spacers are installed in their original positions.
   ⚠Do not torque control arm bolts at this time. They must be torqued with vehicle at ride height.
9. 9

   Connect ball joint to knuckle
   Lower or raise the floor jack supporting the knuckle to align the ball joint stud hole in the knuckle with the ball joint stud on the new control arm. Insert the ball joint stud through the knuckle and install a new or reusable ball joint nut. Tighten the ball joint nut to specification using an 18mm socket and torque wrench.
   Torque spec

   Ball Joint Nut119 Nm (88 lb-ft)
10. 10

    Reinstall wheel and lower vehicle
    Remove the floor jack from under the knuckle. Reinstall the rear wheel and hand-tighten the lug nuts in a star pattern. Lower the vehicle until the tires are just touching the ground but the suspension is not yet compressed. Torque the wheel lug nuts to specification in a star pattern.
    Torque spec

    Wheel Lug Nuts183 Nm (135 lb-ft)
11. 11

    Torque control arm bolts with vehicle at ride height
    Lower the vehicle completely to the ground so that the full weight of the vehicle is on the suspension at normal ride height. This loads the bushings in their neutral position. Using a 16mm socket and torque wrench, torque both control arm mounting bolts (forward and rear) to specification. This is critical for proper bushing life and alignment.
    ⚠Control arm bolts MUST be torqued at ride height with vehicle weight on wheels. Failure to do so will cause premature bushing failure.
    Torque spec

    Control Arm Bolts165 Nm (122 lb-ft)

Reassembly

1. Ensure all fasteners are torqued to specification
2. Verify ball joint nut is properly seated and torqued
3. Double-check that control arm bolts were torqued with vehicle weight on wheels

Verification

• Test drive vehicle at low speed and verify no clunking or unusual noises from rear suspension
• Check that rear suspension ride height appears normal and even side-to-side
• Schedule a four-wheel alignment immediately, as rear suspension geometry has been altered
• After 50-100 miles, re-check torque on control arm bolts and ball joint nut

Related trouble codes on this vehicle

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