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BMW Thrust Arms

Author : bmwe34.net Posted on : 03/12/2004
Model : BMW, 5 - Series (E34) 1989-96 Category : Suspension - Bushings
Source : http://www.bmwe34.net
 


On the BMW E34, E28 and E32, upper control arms, also called thrust arms are attached to the subframe through bushings and to the steering arms by ball joints. The bushings are well known for failure because they take most of the load in the front end under braking and may cause the car to shimmy if worn.Shaking of the front end is often cause by worn thrust arm bushings.

Please if you love your BMW use Lemforder (OEM) parts only!!!! Else you will change your arms every year...

Failure syndromes:
- The 50-60 Mph shimmy.
- Severely enhanced brake shimmy.
- Clunk noise (cause by defective ball joint).
- Bushings torn or with small cracks.


You might want to change the whole arm instead of just changing the bushing if the ball joints are worn. Bushings must be pressed into the arm.


Procedure
  • 22mm wrench, socket and ratchet.
  • Pickle fork (can be loaned from Pep Boys free) and hammer or tie-rod puller.
  • WD 40.
  • Ramps to tighten the bushings.
  • New self locking nuts.

    1. Raise the front of the BMW E34, support with jacks and remove the wheel.
    2. Break the two 22mm nut on the ball joint and on the bushing side.

    I change the whole arm (I can damage the rubber boot):
    3. Use a pickle fork (it works fine) to remove the ball joint. Or use a tie-rod puller.

    I keep my thrust arm (I cannot damage the rubber boot):
    3. This is a little bit harder, you will need to put the nut back (not all the way) to protect the threads in case of a bad blow. Use a hammer to tap the ball joint carrier while applying upward pressure to the control arm. Sounds tricky but you are not hitting the thrust rod or the ball joint but the metal were the ball joint goes through. Applying in the mean time a lot of upward pressure with a pry bar causing the ball joint to pop out. Or use a tie-rod puller. It can be done with a pickle fork, but it is hard not to damage the boot.

    4. Undo the 22mm nut and bolt attaching the thrust arm to the frame. Remove the thrust arm.
    5. If the ball joint turns while tightening the nut, use vice grips or pliers to hold the bottom of the ball joint to the steering plate.
    Installation is reverse of removal but don't tighten the 22mm nut holding the arm to the frame all the way. You will need to lower the car to the ground to tighten the thrust arm bushing nut under load (127 Nm, 90 ft-lb). If you have ramps it is time to use them.

    E32 750il bushings
  • BMA: 2 German arms + 750 bushings pressed: $180
  • Bavauto: 2 arms with performance bushings: $289.
  • BMW: 2 arms no bushings: over $400 (always makes me laugh...)

    Thrust arm bushings should always be changed in pairs. You will need a press or find a shop with a press if you are not changing the whole arm.

    The BMW 750il and 850i have a stronger heavier bushing designed for the greater weight of the BMW 750 and 850 front end and engine. They give a firmer tighter suspension feel and steering response. I would not change them until you have problems with your existing bushing.If you have a fair number of miles on your car when you do change them you may as well do the arm and the bushing, since half the time the ball joint is worn also.

    Note from Dan Pitts

    Thanks for the information concerning how to replace thrust arms. One thing that may be helpful in the procedure is jack up the wheel to take some load off of the ball joint before trying to separate the ball joint from the wheel assembly. I had two pickle forks completely wedged under the ball joint with no movement. I reluctantly put the wheels back on (but not the 22mm nut) and backed out of the garage to prepare for a disgraced drive to the mechanic, when the ball joint popped out. I then replaced the left thrust arm and resumed work on the right side after this moment of joy, but this time I placed the jack under the control arm ball joint and took the load off of the thrust arm ball joint. This time, the ball joint came right off using the pickle fork (actually I used two due to the thickness of the boot). Anyway, thanks for the procedure and the tip on replacement parts.


    Part bumbers

    All BMW E34s

    BMW Thrust arm Left/Right: 31 12 1 141 097/098
    BMW 750i bushings: 31 12 1 136 607
    •  

    Pictures

    Picture 1
    Picture 2

    Click on the thumbnails to see larger images.

     

    References

  • http://www.bmwe34.net
    •  


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