Steering Box Adjustment

Adjustment of the recirculating ball steering box on the W111 chassis to eliminate excessive play in the steering wheel while maintaining smooth operation without binding.

Warnings

Tools required

Parts

• Steering box adjustment screw locknut × 1 — A000 460 00 40 (if damaged)

Fluids

• Hypoid gear oil SAE 90 (for top-up if needed) — 0.25 qt

Preparation

1. Park vehicle on level ground and apply parking brake firmly
2. Chock rear wheels securely
3. Allow engine to cool if recently driven
4. Clean area around steering box to prevent dirt contamination during adjustment
5. Inspect steering linkage for worn components (tie rod ends, idler arm, center link) that could mimic steering box play

Procedure

1. 1

   Measure initial steering wheel play
   Sit in driver's seat and measure free play at the rim of the steering wheel with front wheels pointed straight ahead. Gently rotate the steering wheel back and forth without moving the front wheels. Acceptable play is 10-20mm (approximately 3/8 to 3/4 inch) at the wheel rim. If play exceeds 25mm (1 inch), adjustment is required. Note the current amount of play for comparison after adjustment.
2. 2

   Locate the steering box
   Open the hood and locate the steering box mounted on the left side (driver's side) of the frame rail, just behind the front wheel. The steering box is a cast iron housing with the steering column entering from above and the Pitman arm exiting downward. For better access, the vehicle may be raised and supported on jack stands, though adjustment can be performed from above.
3. 3

   Check steering box oil level
   Locate the oil filler plug on top of the steering box (17mm hex head). Clean around the plug, then remove it with a 17mm wrench. Oil level should be visible just below the threads of the filler hole. If low, top up with SAE 90 hypoid gear oil. Low oil level can cause increased wear and noise. Reinstall filler plug finger-tight for now.
4. 4

   Locate the adjustment mechanism
   On the top or side of the steering box housing, locate the worm shaft thrust bearing adjustment screw. This is a large slotted screw approximately 25-30mm diameter, secured by a locknut (typically 19mm). The adjustment screw has a large slot for a flathead screwdriver and controls the preload on the worm shaft bearings. The locknut may be recessed or covered by road grime.
5. 5

   Loosen the adjustment screw locknut
   Using a 19mm wrench, loosen the locknut on the adjustment screw. Turn counterclockwise approximately 1-2 turns. Do not remove the locknut completely. If the locknut is seized, apply penetrating oil and allow to soak for 15-30 minutes. The locknut must be loosened before any adjustment can be made.
6. 6

   Perform initial adjustment
   Using a large flathead screwdriver that fits snugly in the adjustment screw slot, turn the screw clockwise (tightening) in very small increments, approximately 1/8 turn at a time. This increases preload on the worm shaft and reduces steering play. After each adjustment increment, stop and test steering feel. The adjustment is extremely sensitive—small changes have significant effects.
7. 7

   Test steering throughout full range
   After each adjustment increment, rotate the steering wheel slowly through its complete range from full left lock to full right lock. The steering should move smoothly without binding or tight spots at any position. Pay particular attention to the center position and the extreme lock positions. If any binding is detected, immediately back off the adjustment screw counterclockwise by 1/8 turn.
8. 8

   Check center position feel
   With wheels pointed straight ahead, check that the steering wheel can be rotated gently back and forth with no binding. The goal is to eliminate excessive free play while maintaining smooth operation. There should be slight resistance to movement but no hard spots or binding. Continue fine-tuning the adjustment screw in small increments until optimal feel is achieved.
9. 9

   Verify final adjustment
   Once adjustment feels correct, measure steering wheel play again at the rim with wheels straight ahead. Play should now be 10-15mm (approximately 3/8 to 5/8 inch). Rotate the steering wheel through several full lock-to-lock cycles to verify smooth operation throughout the entire range. If binding occurs at any point, loosen adjustment slightly.
10. 10

    Tighten the locknut
    While holding the adjustment screw firmly in position with the large flathead screwdriver to prevent rotation, tighten the 19mm locknut. Torque the locknut to 35-40 ft-lbs. It is critical to prevent the adjustment screw from rotating while tightening the locknut, as this will alter the adjustment.
11. 11

    Recheck adjustment after locknut torque
    After torquing the locknut, immediately recheck the steering wheel play and feel. Sometimes the adjustment changes slightly when the locknut is torqued. If play has increased or binding has occurred, loosen the locknut and readjust, then retighten. Repeat until adjustment remains correct after locknut is fully torqued.
12. 12

    Reinstall oil filler plug
    Ensure the steering box oil filler plug is installed and tightened to 15-20 ft-lbs using the 17mm wrench. Check for oil weepage around the plug and adjustment screw area. Wipe away any spilled oil.

Reassembly

1. Ensure oil filler plug is securely tightened
2. Clean any spilled gear oil from the steering box housing and surrounding components
3. If vehicle was raised, lower it safely from jack stands

Verification

• Start engine and verify steering operates smoothly at idle (engine running reduces steering effort slightly due to vibration)
• With vehicle stationary, verify steering wheel can be turned lock-to-lock without excessive effort or binding
• Measure final steering wheel play: should be 10-15mm at the wheel rim with wheels straight ahead
• Perform a careful test drive at low speed in a safe area, checking for smooth steering response and no binding through turns
• After test drive, recheck steering box for oil leaks around filler plug and adjustment screw
• Verify no unusual noises from steering box during operation
• After 100-200 miles, recheck steering wheel play to ensure adjustment has remained stable

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