1984 Mercedes 300D Upper Control Arm Replacement

I knew (guessed) my upper control arm bushing was shot because whenever I would drive over speed bumps or potholes, the right side front end would make a clunking noise.

Upon inspection on the right side, the tie rod ends and ball joints looked good. However, high up in the wheel well and pinched by a cavity in the wheel well, I could see that a rubber bushing had popped out of what turns out to be the upper control rod.

Bad upper control arm bushing
Bad upper control arm bushing

1. After identifying the bushing is the issue, jack the right front wheel from the frame, either with the jack that came with the car (if able) or a hydraulic floor jack.

 
 
 
 
 
 
Right Wheel Well
Right Wheel Well

2. Remove the right front wheel.

3. You can now see the upper control arm attached to the torsion rod, the inner fender well, and the lower arm that is attached to the axle that holds the brake rotor.
  
upper bushing, ball joint seperation
upper bushing, ball joint seperation

 

 

 

 

 

 

4. Remove the nut holding the lower arm to the Ball Joint on the bottom of the Control Arm.

5. Insert Pickle Fork between the lower arm and the upper control arm. Hammer the end of the fork until it stops bouncing back from the
rubber seal.
6. Push down on the pickle fork until the lower arm pops off of the ball joint. (CAUTION: get a good grip and watch your head!)
7. Now remove the bolt from the front side of the control arm that attaches it to the end of the torsion bar.
 
Control Arm Upper Mount Bolt
Control Arm Upper Mount Bolt

8. In the engine compartment, look for the bolt and nut holding the control arm to the fender well. Look on either side of the battery tray brace. The bolt head will most likely be on the battery side and the nut will be toward front of car. Remove nut and bolt. The bolt is about 4 inches long and wiring harness below battery may interfere with the bolt coming out.

 

 

 

 

 

 

New vs old
New vs old

9. You should now be able to remove the control arm.

10. Once you have the old one out, compare it to the new one before attempting to install it. It might be tough to install the left control arm on the right side or a control arm for a different model.
 
 
Remove protective plastic cover from ball joint
Remove protective plastic cover from ball joint

11. Remove the protective cover from the ball joint end of the control arm.

 

 

 

 

 

 

Align bushing with mount hole
Align bushing with mount hole

12. Install one of the torsion bar control arm bushings on the torsion bar.

13. Raise the control arm up to the gap in the inner fender well with the ball joint facing down and pointing out while aligning the large hole with the torsion bar.

14. Align the hole of the upper bushing with the mount hole in the engine compartment. If they are a bit off while holding the control arm in place, maneuver the bushing hole with a screw driver or punch until it looks close enough to push the bolt in place.

15. Even though the bolt was originally installed from the battery side, I reinstalled the bolt from the front and placed the nut on the back.

16. Snug the nut for now.

Push up on torsion bar with jack and extendion
Push up on torsion bar with jack and extension

17. Now, with the right frame of the car resting on a jackstand, use your jack with about a foot and a half 4×4 standing on the jack pad. This should be long enough to push up on the torsion bar to be aligned straight with the control arm/torsion bar rubber bushings. If you don’t do this, the forward bushing will most likely get pinched by the retaining washer.

18. Now place the forward torsion bar control arm bushing on the torsion bar. The control arm should now be sandwiched by the two rubber bushings.

19. Place the large bushing retainer, then the smaller washer (the smaller one should fit perfectly against the larger one) on the torsion bar and start threading the bolt in the end of the torsion bar. Again, just snug the bolt. We will make final torque on all bolts and nuts after we have them all started.

20. Now you can lower the jack. Try to aim the ball joint stud into the lower arm mount hole. It should drop down far enough to get the nut started. Go ahead and torque the nut on to the ball joint stud. It will look like it does not get tight enough or is missing a washer, but that is ok. This is normal as the stud is tapered. This is the reason you have to use the pickle fork to separate the ball joint and lower arm (and tie rod ends for that matter).

21. Make final torque on the torsion bar bolt and then the upper mount bolt and nut.

Finished
Finished

22. Reinstall the wheel and air cleaner and you are done.

I found that most parts were very competitively priced when buying from partsgeek.com. The greatest advantage to buying from them is when you buy several parts at the same time because the shipping is always $6.95.

 

 

 

 

 
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3 Replies to “1984 Mercedes 300D Upper Control Arm Replacement”

  1. Thanks for the upper control arm help! I used it to help me replace the upper ball joint/control arm on my ’83 300 D. Simple as pie!!! Now the lower ball joint.

    Thanks again!

    Mark

    1. Hi,
      Rockauto has uppers like mine for under $19 (SKP) or under $29 (MOOG). If you want to do the whole front end, they even have a front end kit for $140 which includes the 2 control arms (URO parts). You might be able to find them cheaper elsewhere and not sure about Rockauto’s shipping price.

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