Subframe Bushing

Replace worn subframe bushings on the front or rear subframe to restore handling precision and eliminate clunking noises during suspension articulation.

Warnings

Tools required

Parts

• Subframe bushing kit (front or rear, specify location) × 1 — Use OEM specification
• Subframe mounting bolts (if corroded or damaged) × 4 — Use OEM specification
• Thread locker (medium strength) × 1 — Loctite 243 or equivalent

Preparation

1. Park vehicle on level ground and engage parking brake. Place wheel chocks behind rear wheels if working on front subframe, or front wheels if working on rear.
2. If equipped with Active Body Control (ABC), use diagnostic tool to depressurize the hydraulic suspension system.
3. Disconnect negative battery terminal to prevent electrical issues during work.
4. Raise vehicle using floor jack at designated jacking points and secure on jack stands rated for vehicle weight.
5. Remove wheels from the axle where subframe work will be performed.
6. Spray all subframe mounting bolts, control arm bolts, and fasteners with penetrating oil and allow to soak.
7. Take photos of all component positions and routing of brake lines, ABS sensors, and wiring for reassembly reference.
8. Position transmission jack or subframe support stand under subframe center, but do not lift yet.

Procedure

1. 1

   Disconnect suspension components from subframe
   Remove sway bar link nuts from both sides using an Allen key to hold the shaft while loosening. Disconnect lower control arms from the steering knuckles by removing ball joint nuts. Use a ball joint separator tool to release the taper fit without damaging the boots. Mark the position of eccentric adjustment bolts if present for alignment reference.
   Torque spec

   Sway Bar Link Nuts55 Nm (41 lb-ft)

   Ball Joint Nut119 Nm (88 lb-ft)
2. 2

   Disconnect steering components and brake lines
   If working on front subframe, disconnect the steering rack from the subframe by removing mounting bolts. Support the rack with mechanic's wire to prevent stress on steering shaft or hydraulic lines. Carefully release any brake line brackets or ABS sensor wiring attached to the subframe. Do not disconnect hydraulic brake lines unless absolutely necessary.
3. 3

   Remove exhaust system supports
   Disconnect exhaust hangers and supports that attach to the subframe. On the S65 AMG V12, the exhaust routing is complex; you may need to lower exhaust sections to gain clearance for subframe removal. Support exhaust components with jack stands or wire to prevent damage to catalytic converters or flex joints.
4. 4

   Support powertrain if removing front subframe
   If working on the front subframe, the engine and transmission are partially supported by it. Use an engine support bar across the fender wells or place a jack with wood block under the oil pan to support powertrain weight. Ensure support is stable before proceeding. For rear subframe work, support the differential housing.
   ⚠️The 6.0L V12 BiTurbo engine weighs approximately 550 lbs. Ensure adequate support capacity before disconnecting subframe mounts.
5. 5

   Disconnect control arms from subframe
   Remove the bolts securing the front and rear control arms to the subframe mounting points. These are large fasteners and may require significant force. Keep track of washers, shims, and eccentric bolts as their position affects alignment. Support control arms with wire to prevent hanging on brake lines or CV axles.
   Torque spec

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

   Remove subframe mounting bolts
   Locate all subframe-to-chassis mounting bolts (typically 4-6 depending on design). These are large diameter bolts. With the transmission jack supporting the subframe weight, carefully remove the mounting bolts. Lower the subframe slowly and evenly, checking for any remaining connections. Guide wiring harnesses and brake lines clear as the subframe descends.
   ⚠️The subframe weighs 80-120 lbs and supports additional components. Ensure transmission jack is centered and secure. Lower very slowly to prevent sudden drops.
7. 7

   Remove old bushings from subframe
   With subframe on a workbench or stable surface, inspect all bushing locations. Use a hydraulic press with appropriately sized bushing removal tools to press out old bushings. The bushings are interference-fit and may require significant force. Note the orientation of any asymmetric bushings before removal. Clean bushing bores thoroughly with wire brush and inspect for cracks or damage.
8. 8

   Install new bushings
   Apply a thin film of soapy water or bushing installation lubricant (never grease or oil) to the bushing outer diameter and bore. Position new bushings with correct orientation, noting any offset centers or alignment marks. Use hydraulic press with proper support cups to press bushings fully into bores until seated. Ensure bushings are not cocked or damaged during installation. Verify each bushing is fully seated and oriented correctly.
9. 9

   Reinstall subframe to chassis
   Position subframe on transmission jack and raise into position, carefully routing all wiring and brake lines. Align subframe mounting holes with chassis. Install new or cleaned mounting bolts and start all bolts by hand before tightening. Tighten mounting bolts in a cross pattern to the specified torque. If no specific torque provided for subframe bolts, consult service documentation as these are critical structural fasteners requiring precise torque.
10. 10

    Reconnect control arms and suspension components
    Reconnect front and rear control arms to subframe mounting points, installing bolts finger-tight initially. Reconnect ball joints to steering knuckles and install new ball joint nuts. Reconnect sway bar links. Do NOT final torque control arm bolts yet; these must be torqued with vehicle weight on suspension at normal ride height.
    Torque spec

    Ball Joint Nut119 Nm (88 lb-ft)

    Sway Bar Link Nuts55 Nm (41 lb-ft)
11. 11

    Reconnect steering and brake components
    Reinstall steering rack to subframe if previously removed, torquing mounting bolts to specification. Reattach all brake line brackets and ABS sensor wiring to subframe mounting points. Inspect all brake lines for damage or interference. Reconnect exhaust supports and hangers.
12. 12

    Reinstall wheels and lower vehicle
    Install wheels and torque lug nuts in star pattern to specification. Carefully lower vehicle from jack stands to ground. Remove jack stands and lower vehicle completely so full weight is on suspension. Rock vehicle side-to-side to settle suspension into normal position.
    Torque spec

    Wheel Lug Nuts183 Nm (135 lb-ft)
13. 13

    Final torque control arm bolts with weight on suspension
    With vehicle weight fully on wheels, final torque all control arm bolts to specification. This is critical as control arm bushings must be torqued at normal ride height to prevent binding and premature wear. Double-check all fasteners including ball joint nuts, sway bar links, and any other suspension components disturbed during the procedure.
    ⚠Control arm bushings will fail prematurely if bolts are torqued with suspension hanging or at full droop. Vehicle weight MUST be on wheels.
    Torque spec

    Control Arm Bolts165 Nm (122 lb-ft)

Reassembly

1. Reconnect battery negative terminal.
2. If ABC suspension was depressurized, use diagnostic tool to repressurize system and bleed any air.
3. Test drive vehicle at low speed in a safe area to verify no unusual noises or handling issues before proceeding to alignment shop.
4. Apply medium-strength thread locker to non-critical fasteners if specified by service manual.

Verification

• Verify all suspension components move freely without binding through full range of travel.
• Check that all fasteners have been torqued to specification, especially critical safety items like ball joints and control arm bolts.
• Inspect for any fluid leaks from brake lines, power steering, or ABC hydraulic system if disturbed.
• Perform four-wheel alignment at a qualified shop with experience on Mercedes-Benz vehicles. The S65 AMG requires precise alignment for proper handling.
• Road test vehicle and verify improved handling, elimination of clunking noises, and proper steering response.
• After 50-100 miles, re-torque all suspension fasteners to verify no loosening has occurred.

More procedures for this vehicle