Jeff N.

I have an interesting noise in the rear suspension on the car. It's a distinct thunk / popping type sound that is mostly likely to occur on a heavy roll loading of the car.

For example, if in an auto-x slalom and rapidly transitioning right - left - right - left, you can get a pop, pop, pop sound. Also, if in a high load high speed sweeper on the track and you get to a certain loading, you can get a single pop.

Mostly seems to occur when you load the right side of the car. Not sure it does it on unload. No jump in the car set when it occurs.

Car setup: 86, 30mm torsions, weltmeister springplate bushings, weltmeister subframe bushings, koni sport, 19mm rear sway, factory droplinks.

CV joints are good, tranny mount - factory - is good. Drop links look good. Sway bar mounts all look good, tight. Bolts for the subframe mounts tight, no apparent signs of movement. Springplate arms (adjusters, toe) all look tight.

Sooo...any suggestions? Not much in the archives to go on. Some suggestions of torsion bar problems or spring plate movement issues.

Thanks!

Jeff

mikey_audiogeek

Same here. More details to follow.

Cheers,
Mike

mjensen

I had a strange/similar noise in my race car that I could only hear turning in the pits. I ended up tightening the rear bumper bolts and noise diminished. Also, Look at the spring plates that have the small rubber "blocks" that cushon the plate to the chassis, located just to the rear of the upper shock bolts.

mikey_audiogeek

OK here goes. Exactly the same symptoms. Noise was there before, during and after doing the following mods:
Torsion delete c/over conversion
Polybronze spring plates
Racer's Edge torsion carrier solid bushes
Transaxle mount upgrade
CV joint maintenance
Sway bar removal

Clunk sometimes happens driving away after having the handbrake on. Clunk only happens under large articulation or high G's. When cornering, the clunk will happen only when changing direction of turn - eg will happen on a fast RH turn but not the following RH turn but will happen on the next LH turn and then will happen again if the LH turn is followed by a RH turn. Most of the time it is Clunk-clunk ie seems to be two components taking a set.

Problem has been present for the last 100,000km and doesn't seem to be getting worse or causing any problems.

Best guesses at this point:

Handbrake shoes sliding sideways
CV's
Output flanges on transaxle (these have quite a bit of axial play)
Fuel tank?

Jeff N.

Interesting. I *think* my problem started after I did my upgraded.

Mikey - my noise is distinct thunk/pop. It's like something it torquing up and then letting go. It does sound very much like your noise. Just on a wild lark - any chance you have a bolt in cage? I was also wondering if this might be due to body flex and the cage points moving...?

Matt - what are the rear bumper bolts? Is that part of the suspension or (duh?) part of the rear impact bumper?

86 951 Driver

I have the same thing. It almost sounds like a suspension mount is bad and it rattling sort of. I have been told it is most likely my CV's. Because it is only when my car squats a little bit under acceleration. It makes the noise bad.

dillon410021

could it be the exhaust hitting the suspension(torsion bar tube)?

beebone

Mine got the same problem but on the front axle, since the new RE Delrin bushing, ball joint rebuilt, 968 caster block. The sounds like "bunk bunk bunk" on each pumpy movement. Slight bumpy or smooth road got no problem.

Jeff N.

Haha...no thread hijack here. This is rear clunks only. Go get your own thread!

Jeff N.

Interesting thought - don't think so but I can't 100% rule it out. Here's why I don't think so.

- Sound is heavy/solid and seems like it's coming thru the chassis. Not a tinny sound you might expect hitting the exhaust.

- It's very load specific. Seems like you need to get a certain amount of torque on the suspension and then something quickly "adjusts" or "slips" or "moves". At this point you get the thunk. Maybe something is moving and hitting the exhaust but the sound isn't right for that as per the above.

951kaos

I have a similar sound from my rear suspension. It is usually quiet on the highway; when you put it on the track or some tight twisty turns you hear the pop/thunk sound.
I had the following work done on the rear suspension last year: torsion bars removed; Bilstein Escort Cup shocks with 2.25"x7" - 500lb springs with spacer springs; aluminum upper torsion tube mount; polybronze spring plate bearings; Weltmeister torsion tube bushing mounts; delrin trailing arm bushings; Weltmeister swaybar.
Had the shop that did the install look at the rear suspension prior to this season of track events and found all suspension points were tight/retorqued. They suspect it to be my spherical bearings on the swaybar links making the noise.
I think the noise is coming from the Weltmeister torsion tube bushing mounts; as the sound seems to come from right behind me/driver or passenger. Could the solid plastic/delrin torsion tube bushings compress a bit or move a bit under loading? I have not had time to try a dry film/silicone lubricant on those bushings to see if it makes any change in noise.

superloaf

i've had the same thing going on for a few years now and posted many times on here with no results. (i'm surprised so many other people have chimed in with similar problems.) mine is definitely load specific as it seems that when the weight transfers, it will pop. best guess is torsion bar bushing or something like that. and my suspension is basically stock. i have replaced the tranny so i can't rule that out (mount or something loose) but i still think it's the torsion bars because of the way it feels although some of those above without TB's have a similar problem too. wonder if we're having different problems?

86 951 Driver

Has anyone replaced their CV's and the sound goes away?

Jeff N.

On my car, the CV's are tight. Also, on my car, it doesn't have the characteristics of a bad CV. Typically, a bad CV will vibrate at speed and may creak/groan/crunch when driveline load is applied. Tends not to be cornering related.

The problem we are trying to sort is related created by significant cornering loading of the aft suspension. You could very well have both problems...bad CVs and the pop. Not sure they would be related.

951kaos

Also, my cars rear suspension was quiet with no noise when it was stock with torsion bars; original rubber bushings; Koni shocks and Weltmeister sway bar. It was quiet after the mods for a while and then got noisy after a spririted long drive. I do believe it has to do with the replacement mounting bushings on the torsion tube. Sometimes the noise gets very annoying