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Discussion Starter · #1 ·
Hello All:

Following my encounter with a guard rail last spring, I finally got around to replacing Bella's trailing arm, anti-roll bar and reaction triangle bushings with OEM units. Things went well on the street, but after two vigorous autocross events, I picked up a clunk on acceleration from the rear end. Finally got under this week, and the first thing that caught my eye was a twisted trailing arm on the right side. The top of the arm is ****ed inboard so much that the bushing housing at the rear is almost making contact with the arm. A block of wood and trolley jack puts everthing right, but the jack can't keep up as I go down the road. Waiting for the spouse to return from PA so she can "clunk" the drive line while Bella's rear end is up on ramps (yes, I'll invite Channel 4 to drop by, just in case:)).Also checked everything I could get a hand on for slack (includidng fasteners), and things seem nominal. "Search" turned up 415 hits on my subject line, so I once again turn to the BB's collective intelligence.

Also, I keeping with my rant of several months ago, I solemnly promise to provide full disclosure on the outcome of this situation.

Also, also, added tags for the benefit of future serchers.

Thanks in advance.
 

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Discussion Starter · #2 ·
Re-sub inquiry

My question of 11/14 is slowly disappearing into the "Gorge of Eternal Peril", leaving me only the unpleasant option of responding to my own post, thereby bumping the query back to the top of the list:).

The "clunk" is something I'm sure I can resolve, but my primary concern is with the twisted trailing arm. Is there a lot of this going around? What are the consequences? Anybody?

Also, that "thumbs down" emoticon sure looked like a question mark when I first clicked on it. My bad.
 

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I had a 'clunk' from under the rear of our '84 Spider. Turned out the anti-roll bar was slightly displaced to one side and, on going over a big enough bump, it would touch the underside of the body. I loosened the mounts, pried the ARB to re-position it and secured the mounts. No more thumps (from under the car - I still get one on the back of the head if I go too fast with my wife in the passenger seat...)

Anyway, is the trailing arm itself twisted or are the bushings ****-eyed?
 

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A photo of the twisted trailing arm might be helpful. Did I read your initial posting to say that two, new trailing arms were installed following the accident, and now one of them has become twisted?

750/101 series Alfas have a similar rear suspension design, and they tend to twist the trailing arm mounting brackets on their axles. This happens because the Alfa suspension doesn't allow the body to roll much relative to the differential - only the compliance of the F and R trailing arm bushings allow movement in that degree of freedom.

Alfa improved this design on the 105/115 series cars with much heavier trailing arm brackets on the axles, and a "U" cross section for the arms that allows them to twist a bit without permanent deformation. However, your's obviously got twisted too much!

How are your limit straps? If the straps are missing or too long, they might have allowed the differential to drop too far relative to the body, twisting the trailing arm. Or, is something still tweaked following your accident?
 

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Discussion Starter · #5 ·
Steve tells all...

Alfajay:

Thanks for getting back in touch. My original post should have been worded better...all original suspension hardware remains, but new OEM bushings (OEM) were installed for anti-roll, front and rear of trailing arms and reaction triangle to differential. Once again, looking from the rear, the right trailing arm is twisted counter-clockwise, with the bushing housing, where the cylinder extends through the U-shaped arm, almost touching the anti-roll/rear trailing arm mount. (Sorry I had to go with the thousand words vs picture). Will post a photo when the camera gets home tomorrow.

The limit straps are intact, and although my bounce off the guardrail was a solid hit, I don't think there are remaining implications...the reaction triangle went in and out without a struggle, so I'm thinking the frame is reasonably straight.

If trailing arms twist past their elasticity limit, can they be removed and straightened or are they toast? You suggested an excessively extended axle (due to too much slack in the limit straps), combined with extreme rotation of the car at autocross (I did spin 360 degrees on right hand turns twice) could cause the lightly loaded right side trailing arm to twist. Also noticed I may not have completely tightened the R.T./differential bushing, which may have contributed to excess L/R axle motion. Now I'm just thinking out loud.

Anyway, starting to look like a new right side TA. Just don't want to have the same thing happen again, so I've got to get to the bottom of that issue. Will be exploring the "clunk" situation when spouse returns.

Jump in anywhere.

Cheers, Steve
 

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Steve:

I don't have any other ideas on this one.

I would assume that a twisted trailing arm could just be bent back into shape. But as you say, how to prevent it from bending again?

The other thing that has me puzzled is that as the body rolls relative to the rear axle, both trailing arms see the same amount of twisting. So, why would one deform, and not the other? Strange.
 

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Discussion Starter · #7 ·
Alfajay:

You're right about the loads seeming to be equal on the trailing arms. One twists, one doesn't?

If I keep blathering about this long enough, thereby keeping it on page one, someone more knowledgable than me will go for the bait and respond. Got the camera...film at 11.

Steve
 
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