I had my first go at replacing the thrust and control arms on my '94
540iA this evening. The balljoints on the control arms are gonzo and
the thrust arm bushings are shot (60 mph braking shimmy) so I figured
I'd replace both arms (on both sides obviously) and refresh the front
suspension. With 115k miles on them they don't owe me anything.
So anyway, everything looks fairly straight forward *except*... How the
heck are you supposed to remove the Bolt and Nut at the bushing end of
the Thrust arms? The bolt head is easily accesable, but there is no way
I can get any kind of wrench on the nut end. It's wedged in behind and
between the round section cross-member and frame so tightly that I can't
even get an open end wrench on it to hold it and try to spin the bolt,
though that would be a less than desireable method.
Anyone done these on a 540 before? I'm guessing from the descriptions
I've read online and in my Bentley that there is more clearance in that
area on the 6 cylinder models or in other years. They don't mention
doing anything fancy or having to remove anyuthing to gain access to the
The only thing I can see doing is removing the sway bar mount bracket
and moving the bracket and sway bar down and out of the way? Of course
that bolt would not budge for me and I don't have an impact wrench
(yet), but that may be my next purchase... ;-)
The only advice I received here (alt.autos.bmw) was to consult the
bimmer.info forums, which I did. And I did get some good advice from a
number of folks that had done this job before. I am posting my thanks
and appreciation there, but also wanted to post a follow-up here as
well, as a means to capture the answers for posterity.
First off, it seems that some flavors of the E34 (later years only?
8-cylinders only?, not sure...) got an additional cross member. This is
a bent, round section of frame that goes across from one thrust arm
bushing mount to the other. It appears to do little other than possibly
shore-up any frame flex due to force from the thrust arms? The cross
member is item #1 in this illustration:
The large bolt for this cross member (13), also goes through the plate
that the stabilizer bar mounts to (12). Dropping the cross member is
the key to getting access to the nut on the end of the thrust arm
bushing bolt (11).
In my case, I went out and bought a new craftsman 6 point, 18mm 1/2"
drive socket because the 18mm socket I had already was a 12 point. I
had given it one try already and realized I would need to use more force
than I was comfortable putting on the 12 pointer. Good thing I chose
craftsman because, after slathering the bolts with PBblaster, the left
side cracked loose pretty easily. The right side cracked too, but it
was the socket that cracked this time. Ooops... Back to Sears
Essentials (used to be K-mart) for a free replacement.
With my replacement socket in place, I heated the crap out of the bolt
and was finally able to get it to budge. Whew!! Thought I was finally
going to have to buy that air compressor and impact gun that I've always
I did not actually have to remove the cross-member entirely. I just
loosened the large bolt about 1/2" which allowed me to get a box-end
wrench over the nut and crank on the bolt head from the other end.
After the new thrust arms and control arms were installed, I left this
crossmemeber loose until after the I had tightened the bushing bolts to
spec with the wheels back on and the suspension loaded. A good set of
ramps are worth their weight in gold for that task.
How did it come out? Great. It really tightened up the front end and I
don't get any braking wobble anymore. The steering has even tightened
up. What I assumed was accumulated slop in the steering gearbox has
By the way, you could not tell that there was anything wrong with the
Thrust Arm bushings just by looking at them. They looked fine. The
wobble symptom was the only clue. But the balljoints on the control
arms were bad (visibly and audibly) and the braking vibes at 50-60 mph
told me it was time for them to go too.
The cross member connected to the thrust arms is on my 95 525i too. So
I believe it is on all e34 w/m50 and m50tu engines. I recently did the
entire ball joint set. Impact wrench makes the job much, much easier.
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