U-Joint

Replace worn universal joint(s) on the rear driveshaft of a Mercedes-Benz S65 AMG, ensuring smooth power delivery and eliminating vibration.

Warnings

Tools required

Parts

• Driveshaft U-joint × 1 — Use OEM specification
• U-joint strap bolts (if reuse not recommended) × 4 — Use OEM specification
• Differential fluid (if drained) × 1 — Mercedes-Benz 75W-85

Preparation

1. Park vehicle on level surface, engage parking brake, and place wheel chocks at front wheels
2. Allow exhaust system to cool completely if vehicle was recently driven
3. Raise rear of vehicle and support securely on jack stands at approved jacking points
4. Remove rear wheels if needed for better access (optional but recommended)
5. Inspect driveshaft for wear, play, and confirm U-joint replacement is necessary

Procedure

1. 1

   Mark driveshaft alignment
   Use a marker or paint pen to mark the relationship between the driveshaft and the rear differential flange, and between the driveshaft sections if applicable. This ensures proper phasing during reassembly and prevents vibration issues. Mark at least two points for verification.
2. 2

   Remove driveshaft mounting hardware
   Remove the four CV bolts connecting the rear of the driveshaft to the differential flange. Support the driveshaft with a strap or transmission jack to prevent it from dropping. If the U-joint is at the differential connection, remove the U-joint strap bolts instead of CV bolts.
   Torque spec

   CV Bolts82 Nm (61 lb-ft)

   Driveshaft U-Joint Straps20 Nm (15 lb-ft)
3. 3

   Support and lower driveshaft
   With driveshaft properly supported, carefully slide it rearward to disengage from the transmission output shaft or center bearing. Lower the driveshaft assembly and remove from vehicle. Take care not to damage the transmission output seal or differential seal during removal.
   ⚠Driveshaft weighs approximately 20-30 lbs. Use proper lifting technique and support.
4. 4

   Secure driveshaft for U-joint removal
   Place driveshaft on a stable workbench. Identify the faulty U-joint. Clean the area around the U-joint thoroughly with parts cleaner. Note the orientation of the U-joint caps and yoke. If equipped with a yoke nut, remove it first.
   Torque spec

   Yoke Nut150 Nm (111 lb-ft)
5. 5

   Remove U-joint retaining clips
   Using snap ring pliers, remove the internal or external snap rings (circlips) that retain the U-joint bearing caps in the yoke. There are typically four snap rings, one for each bearing cap. Keep these if reusable, or discard if replacing with new hardware included in U-joint kit.
6. 6

   Press out old U-joint
   Using a U-joint press or bench vise with appropriately sized sockets, press out one bearing cap at a time. Position a socket larger than the bearing cap on one side to receive it, and a smaller socket on the opposite side to push the U-joint cross through. Repeat for all four caps until the old U-joint is completely removed. Clean the yoke bores thoroughly.
7. 7

   Install new U-joint
   Pack the new U-joint bearing caps with grease if not pre-greased. Insert the U-joint cross into the yoke. Start one bearing cap by hand into the yoke bore. Use the press or vise to carefully push the bearing cap in while aligning the U-joint cross. Install the snap ring in the groove. Repeat for the opposite side, then the remaining two caps. Ensure all snap rings are fully seated in their grooves.
8. 8

   Verify U-joint installation
   Check that all four snap rings are properly seated and the U-joint moves freely without binding. There should be minimal lateral play. The U-joint should articulate smoothly through its full range of motion. If binding occurs, disassemble and reinstall.
9. 9

   Reinstall driveshaft
   Carefully raise the driveshaft assembly into position. Align the front splined end with the transmission output shaft or center bearing, ensuring proper engagement. Support the rear end with your transmission jack or strap. Align the marks made during disassembly to ensure proper phasing.
10. 10

    Connect driveshaft to differential
    Align the driveshaft flange or U-joint straps with the differential companion flange using the alignment marks. Install the CV bolts or U-joint strap bolts finger-tight. Verify alignment is correct before final tightening. If using U-joint straps, ensure they are positioned correctly and evenly.
    Torque spec

    CV Bolts82 Nm (61 lb-ft)

    Driveshaft U-Joint Straps20 Nm (15 lb-ft)
11. 11

    Torque all fasteners
    Torque the CV bolts to 82 Nm (61 lb-ft) in a cross-pattern if applicable, or torque the U-joint strap bolts to 20 Nm (15 lb-ft) evenly. If a yoke nut was removed, torque to 150 Nm (111 lb-ft). Ensure all fasteners are properly seated and torqued to specification.
    Torque spec

    CV Bolts82 Nm (61 lb-ft)

    Driveshaft U-Joint Straps20 Nm (15 lb-ft)

    Yoke Nut150 Nm (111 lb-ft)
12. 12

    Reinstall wheels and lower vehicle
    If wheels were removed, reinstall them and torque lug nuts to 183 Nm (135 lb-ft) in a star pattern. Carefully lower vehicle from jack stands. Remove wheel chocks.
    Torque spec

    Wheel Lug Nuts183 Nm (135 lb-ft)

Reassembly

1. Double-check all fasteners are torqued to specification
2. Verify driveshaft alignment marks were properly matched during installation
3. Confirm no tools or parts were left under vehicle

Verification

• Start engine and observe for any unusual vibrations at idle
• Test drive vehicle at various speeds (30 mph, 50 mph, 70 mph) and listen for clunking, vibration, or unusual noises
• Perform moderate acceleration and deceleration to verify smooth power delivery without binding
• Re-check torque on all driveshaft fasteners after 50-100 miles of driving
• Inspect U-joint area for any signs of grease leakage or component movement

More procedures for this vehicle