What is Up with My Spring Plate Bushing

[gregwils]

I have a "driving me nuts" clunk in my rear suspension that is...well, driving me nuts. It only occurs on hard right hand turns. It is a definite clunk, but the noise sounds like something is binding. If you turn left after it has clunked, it clunks again, but this time like something is unbinding. It will also 'unclunk' if you back up, but only it is in the "binded" state. I made a diy chassis sensor and the clunk sounds like it is coming from the spring plate end- where the t-bar protrudes through the cover.

I have replaced the spring plate bushings twice - once with ERP, then again with Neatrix. I also replaced the spring plate cover - from our host. The noise started after I installed the ERP, but the prior owner had done some funky drilling on one bolt hole in the old spring plate cover. I have owned the car for six years and am just now uncovering it.

The picture you are looking at is a new spring plate cover and believe it or not a two DAY old Neatrix bushing. The gap at the top is about an 1/8th of an inch, the bottom about 3/8ths. It looks to me like a 20 year old bushing. The less than two year ole ERP's looked the same way, so I took them out, but they were obviously not the issue. (Chuck has great products, this is in no way a slight toward ERP, just my desparation for a solution.)

What is wrong with my suspension? Bent t-bar? Bent spring plate? The quarter was replace, but the tub doesn't appear as though it was touched. It just doesn't seem as though things are lined up correctly between the t-bar, the spring plate and the spring plate cover.

Has anyone seen something like this before? I don't know what is wrong, but I know something isn't right.

[gregwils]

Any suspension experts out there with suggestions? What type of issue would prevent a spring plate from centering inside the spring plate cover? Thanks.

[chris_seven]

The bad news may be that the torsion bar tube may be bent. The fact that it has had a bang hard enough to need a new quarter isn't the best news.

If the wheel was hit square on then the tube may buckle slightly and not show up as much damage on the face where the torsion bar cover mounts.

The 'funky' drilling may be a give away.

If the Torsion bar is straight and isn't roughly centred into the tube when looked at 'end on' then it is likely that the tube has deformed.

We have has a couple of old cars where this was the case and we have had to cut the tube and square up the back end.

It does tend to show up in rear end alignment as well and it can be difficult to dial in the suspension.

[ivangene]

maybe someone rotated a worn out bushing and put the "sag" UP ??

needs to come apart to see whats going on

[boyt911sc]

Greg,

Have you checked and inspected very closely the difference between the old and the new covers? Check the alignment before and after installing the 4 mounting bolts. I have a suspicion that they are aligned and centered without the 4 bolts installed. Keep us posted.

Tony

[gregwils]

Thanks Chris. Well, that would not be good news, but sounds like a plausible explanation. It makes sense that it may be related to the impact, and I realize the effect of the impact can sometimes show up elsewhere in the car. The body damage didn't appear that bad, but I guess that if a large chunk of the impact was absorbed by the wheel and suspension, the tube could have been bent.

How can I verify whether or not it is an issue with the tube? Any damage is likely not enough to see with the naked eye. If I pulled both t-bars and inserted a straight rod the entire way through the car to compare the location of the rod exiting the tub on either side, would that help answer whether or on the tube was straight? Also, could the tube be bent back into straight by a shop without removing it from the car?

[gregwils]

Ed - No, they were brand new Neatrix bushings.

Tony - I did lay the old and new covers over one another. The alignment looked correct with the exception of the lower front bolt hole that was hogged out to allow it to move around.

It's Monday AM, so I won't have a chance to work on it for a while. It is possible I may just live with it for a few months and drive it this summer the way it is, then rip it apart this winter. Thanks.

[K Sykes]

Had a similar "clunk". It turned out to be cracked welds on the bosses that the cover bolts go into. Had a body shop re-weld them - Porsche experienced body shop so they aligned things right.

Klunk was gone.. one more thing to check

[chris_seven]

Just check that the Torsion bar is straight and fit it into the tube without bushes.

With one spline engaged in the 'dogbone' in the torsion bar tube the end of the bar should be roughly central.

The last one we had with this problem would build OK with an OEM Bush from Porsche but not with an ER Polybronze.



This one was quite away out but the side of the chassis rail looked OK and it wasn't until we looked very closely at the tube where it joined on the other side of the rail we spotted the buckle.

[gregwils]

Ok, just to clarify. The t-bar should stick straight out of the tube opening without any bushings around it. It will be at least a week until I can get to it, but I will re-post to this thread when I do. Thanks.

[gregwils]

Chris - let me ask you, and the board, one more question. If the tube was bent, would there be a buckle? Or could it be so slight, the tube just bends a few degrees?

[chris_seven]

I have seen two tubes with the same problem which I think was due to an impact on the wheel.

Both resulted in a small kink which was very difficult to see. I think the rear rail had moved slightly but this would be quite difficult to see without a major strip down.

We repaired the damage by fitting a replacement tube but if the misalignment is less you could be ok to cut and re-weld with some bracing.

[gregwils]

I have been thinking about this and am perplexed. I read in another thread about a bent torsion tube that the t-bar had to be pryed back into position to fit the spring plate bushing into the tube. I did not experience anything like that. The spring plate bushing slid directly into place without any guidance, so I believe that the t-bar is centered. Plus, the pressure to compress a new bushing the way mine is compressed would require tremendous force against the bushing. I would have had to have noticed something was screwy. I still need to verify, but based on everything I have read, it seems unlikely a bent torsion tube is the issue.

I am starting to wonder if the spring plate or the banana arm might have some damage. I need to go through the whole dis-assembly/assembly process in sequence to determine when the bushing gets compressed. It must be either occurring when I bolt the spring plate cover to the body or when I bolt the spring plate to the banana arm. I don't remember the cover being difficult to mount, but I don't want to speculate here.

[DaddyGlenn]

Greg, this is baffling. Have you looked at the bushings post clunk but before the unbinding clunk? It would be interesting to see if the clunk results in a visible difference.

[gregwils]

Hey Glenn, I've been following your project. Yes, baffling is a good word. I have not done what you suggested, but have that on my list. Recently, it has unclunked when I backup. I am not sure if it is the change in motion or the spring plate being 'pulled' back. Anyway, I will get a chance to experiment a little this weekend and will do the visual inspection as you suggest.

[DaddyGlenn]

Thinking out loud here..... I'm not so sure about the bent torsion tube idea. While that could lead to a compressed bushing, I don't think you would get movement. The clunk tells me something is moving when it shouldn't. And just having the bushing compressed doesn't cause a clunk for those of us who drove around on 30 year old bushings. I would be concerned that something is broken that allows the torsion bar(s) to move either at the center of the torsion tube or the end. Either way, thT means structural damage. I hope my thoughts are flawed....

[DaddyGlenn]

Originally Posted by K Sykes

Had a similar "clunk". It turned out to be cracked welds on the bosses that the cover bolts go into. Had a body shop re-weld them - Porsche experienced body shop so they aligned things right.

Klunk was gone.. one more thing to check

This fits with my thoughts above.

[steely]

+1 - excellent point (what Daddyglen said about before and after)

I am almost ready to install my new neatrix bushing and reading this with intent. Greg, your first pic looks interesting, but I have a hard time with my own theory that the TB tube is traveling/smacking the SP cover. Dumb question, all of the nuts/eccentrics are tight on the spring plate?

[ben parrish]

Ok...had a clunk years ago..it was a loose transmission mount bolt. Have you checked them and the sway bar mounts?

[gregwils]

Lots of thoughts here, thank you all. I agree the compressed bushing is not the source of the noise, but I am hoping if I can determine what is causing the compression it may lead me to the cause of the clunk. Even if it does not lead me to the clunk, something is not correct in the vicinity of the noise so I feel like I need to fix it. The chassis sensor that I made tells me the noise is definitely coming from the t-bar or spring plate - new motor/trans mounts and noise exists with sway bar removed. Every single nut or bolt anywhere in the vicinity of the rear of the car is set to spec. I have examined the spring plate cover mounting bosses pretty closely, but it could be something not readily visible.

Unfortunately, I agree with your theory on the "something is moving that should not be moving". I haven't ruled out the noise coming from inside the tube. I do most of my own work, but I sometimes use Fast Freddies near Butler, PA. He thought the noise was coming from the center of the tube. My chassis sensor stopped working, but have ordered new stuff to make a few more. My plan is to figure out the bushing and get the new chassis sensor on the car to try to pinpoint the origin.