Mercedes Coupes/Sedans/Wagons 1974-1984 Repair Guide

Steering Knuckle/Ball Joints

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BALL JOINT INSPECTION



See Figures 1 and 2

Click image to see an enlarged view

Fig. Fig. 1: Check ball joint axial play; if it exceeds maximum tolerance, it must be replaced



Click image to see an enlarged view

Fig. Fig. 2: Rock the tire at its top and bottom to check the ball joint radial play

All models of Mercedes-Benz covered in this guide use steering knuckles with ball joints. Most models use a type of ball joint that is maintenance free.

To check the steering knuckles or ball joints, jack up the car, placing a jack directly under the front spring plate. This unloads the front suspension to allow the maximum play to be observed. Late model ball joints need be replaced only if dried out with plainly visible wear and/or play.

REMOVAL & INSTALLATION 1974-76 230, 240D, 280, 280C, 1975-76 300D, 380SL, 380SLC, 450SL and 450SLC Models



See Figure 3

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Fig. Fig. 3: Cross-sectional view of the steering knuckle/ball joint1974-76 230 and 240D, 280 and 280C; 1975-76 300D, 380SL, 380SLC, 450SL and 450SLC models

  1. This should only be done with the front shock absorber installed. If, however, the front shock absorber has been removed, the lower control arm should be supported with a jack and the spring should be clamped with a spring tensioner. In this case, the hex nut on the guide joint should not be loosened without the spring tensioner installed.
  2.  
  3. Jack up the front of the car and support it on jackstands.
  4.  
  5. Remove the wheel.
  6.  
  7. Remove the brake caliper.
  8.  
  9. Unbolt the steering relay lever from the steering knuckle. For safety, install spring clamps on the front springs.
  10.  
  11. Remove the hex nuts from the upper and lower ball joints.
  12.  
  13. Remove the ball joints from the steering knuckle with the aid of a puller.
  14.  
  15. Remove the steering knuckle.
  16.  
  17. Installation is the reverse of removal. Be sure that the seats for the pins of the ball joints are free of grease.
  18.  
  19. Bleed the brakes.
  20.  

190D and 190E Models See Figure 4

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Fig. Fig. 4: Cross-sectional view of the steering knuckle/ball joint used on 190D and 190E models

  1. Raise the front of the vehicle and support it with jackstands. Remove the wheel.
  2.  
  3. Install a spring compressor on the spring.
  4.  
  5. Remove the brake caliper and then wire it out of the way. Be careful not to damage the brake line.
  6.  
  7. Remove the brake disc and wheel hub.
  8.  
  9. Unscrew the three socket-head bolts and then remove the brake backing plate from the steering knuckle.
  10.  
  11. Tighten the spring compressor until all tension and/or load has been removed from the lower control arm.
  12.  
  13. Disconnect the steering knuckle arm from the steering knuckle (this is the arm attached to the tie rod).
  14.  


CAUTION
There must be no tension on the lower control arm.

  1. Unscrew the three bolts and disconnect the lower end of the damper strut from the steering knuckle.
  2.  
  3. Remove the hex-head clamp nut at the supporting joint (lower ball joint).
  4.  
  5. Remove the steering knuckle.
  6.  
  7. Installation is in the reverse order of removal. Please note the following:
    1. Tighten the supporting joint clamp nut to 70 ft. lbs. (125 Nm).
    2.  
    3. Refer to the "Damper Strut Removal and Installation" procedure when connecting the lower end of the damper strut to the steering knuckle.
    4.  

  8.  

Except 190D, 190E, 1974-76 230, 240D, 280, 280C, 1975-76 300D, 380SL, 380SLC, 450SL and 450SLC Models See Figure 5

Click image to see an enlarged view

Fig. Fig. 5: Cross-sectional view of the steering knuckle/ball joint componentsall models except 190D and 190E; 1974-76 230 and 240D, 280 and 280C; 1975-76 300D, 380SL, 380SLC, 450SL and 450SLC models

  1. Jack and support the car. For safety, it's a good idea to install some type of clamp on the frontspring. Position jackstands at the outside front against the lower control arms.
  2.  
  3. Remove the wheel.
  4.  
  5. Remove the steering knuckle arm from the steering knuckle.
  6.  
  7. Remove and suspend the brake caliper.
  8.  
  9. Remove the front wheel hub.
  10.  
  11. Loosen the brake hose holder on the cover plate.
  12.  
  13. Loosen the nut on the guide joint and remove the joint from the steering knuckle.
  14.  
  15. Loosen the nut on the support joint.
  16.  
  17. Swivel the steering knuckle outward and force the ball joint from the lower control arm.
  18.  
  19. Remove the steering knuckle.
  20.  
  21. If necessary, remove the cover plate from the steering knuckle.
  22.  
  23. Installation is the reverse of removal. Use self-locking nuts and adjust the wheel bearings.
  24.  

 
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