I put the Springtech Springs in my '86 and the car looks great. However whenever I hit a bump or a pothole I hear this thunk coming from the rear.

I double checked everything and everything seemed nice and tight. The spring insulators didn't move and neither did the springs. Is there an insulator that goes at the bottom maybe, where the spring meets the axle that may eliminate that sound? I never gave it much thought since stock they didn't have any.

 

I have a similar thunk. Im interested to know what ideas everyone comes up with. I am thinking that its my cat-back system raising up off the hangers and then dropping back down. But it might have something to do with my suspension.

 

Check your upper shock mount; see if it's punched out of the floor pan.

All you have to do is pull out the back seat and peel back the carpet.

 

No, it's not the upper mount since I just changed the shock out as well. It is annoying.
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I used to think the samething myself until I really got down there and tugged on it a few times and there was just no way it could be since the distance from the mounts was just enough that I had to force it to bang into the car.

 

Same issue here, but I wonder if the metal around the upper shock mount is flexing and "popping" making the thunk sound.

Happened right after I put new shocks and struts on too. Drives me crazy

 

One thing I can add is this: I was running KYB GR2's in the rear, a couple days ago, I installed Koni Reds. When the KYB's were fully extended, the rear springs were very loose where I could move them around on the spring perch with my hand. The Koni reds are about 2" shorter than the KYB's therefore wont let the springs get so loose. I havent gotten a chance to drive the car over any speed bumps with the Konis, but I think that between them being much stiffer & shorter, it will limit the travel of the rear & I may have solved the problem. I wont be able to test it for atleast a week.

 

CHECK YOUR TRACK BAR BRACE , I FOUND ON MY 89 RS THAT ALL 3 BOLTS THAT SECURE BRACE TO BODY HAD FALLEN OUT . CURED MY KLUNK . HOPE THIS HELPS .

 

Are them springs lowering springs?

I had a clunk in the rear and it was the panhard bar end had opened up and started rattling.

 

i had the same issue after installing dropzone springs in the rear, sounds almost like a busted shock.

 

If they are lowing springs, its possible your just now hitting your bumpstops where you never were before.

If you didnt re-center the axle, the right tire could be hitting the inner fenderwell.

Panhard bumping on the brace.

Could be several things. I put my car on ramps(not stands!) and had several people start bouncing the rear end tell I found out what it was.

 

Here is the funny part Dale, whenever I bounce the car up and down it is quiet as hell......no thunk! The only thing I was told by another member is they may have a bushing for the bottom of the spring so that metal doesn't touch metal which would make the spring a little tighter and maybe eliminate the clunk. I checked Summit and they have a bunch of different sizes it looks like and they still haven't responded to me which one fits the thirdgen.

 

On the bouncing, maybe they arnt moving it enough is my only guess.

I have no spring on the bottom of mine, have not seen one on the bottom. The only clunking I have is my TQ arm hitting the driveshaft tunnel.

 

Just thought of something... Of the people with this tumping sound... How many have an aftermarket cat-back exhaust. Its possible that the rear axle is hitting the intermediate pipe going over it. Look at the pipe for evidence of contact.

OK>>> Now I am out of ideas

 

I guess it is possible considering the stock pipes are what, 2 1/4"? If you are like me, you upgraded to 3" and when I remember what a pain in the **** it was to get the pipe outta there with little clearance (junkyard special), I could see how it is a problem. I'll check it just for the heck of it next time.

 

There is no stock lower insulator.

JamesC

 

Correct but not stock, aftermarket. Some spring kits do offer them.

 

Interesting. Can you provide a link to one of those kits?

JamesC

 

My car was bone stock when I put the new shocks and struts on and it started doing that. I have no clue, but pulling off a drive way onto a street or making an inclined turn is when it happens for me in the rear.


Like something is binding then just pops and makes a thunk in the back.

 

I'll have to ask my buddy when he comes back from vacation where he got 'em from.

 

If you don't hear anything when your friends bounce on the back remember that everytime you hit a bump the suspension compresses and extends make sure something isn't loose on the rebound travel of the suspension like an upper shock mount not being quite tight enough or a worn bushing on just about anything. it can look ok while sitting on the ground.

 

I hate the snow/salt. Its been two weeks & I haven't been able to take the car out to see if I fixed this problem. GRRRRR!!

 

I've got the same problem. Everything was fine until I put new stock springs and custom built exhaust on. It sounds like it's coming from the right rear, around where the exhaust goes up over the axle. I've got new shocks for it, but unfortunately will have to wait until spring to see if the shocks help at all.

 

Did anybody ever fix this issue? Im stumped. I check all the seams, replaced the shocks, (bushings and springs tomorrow), and it still pops.

 

The larger exhaust,as you are thinking,could be the culprit of the noise.If you go to 3" there isn't room on suspension compression and you get a clunk.BMR makes a panhard upper brace kit(I'm not sure if UMI has one yet).One of it's main purpose is to relocate the brace for clearance.

 

I had this happen to me twice. The first time was one of the rear control arm bolt had loosened a bit. The second time was after I put new shocks in. A week later it started thunking cause one of the bottom bolts had come a bit loose.

When I mean a bit loose, it's like 20ft/lbs less than spec. It's still feels tight when you try to shake the parts by hand, but not tight enough for big bumps

 

I recently installed 2 inch lowering springs on my 83 TA, and immediately I noticed a similar sound, and it turned out to be the parking brake cable where it curves back around the axle on drivers side, it was catching on the axle parts and would pull taught and release making the sound. I tied it up and the sound is gone.

 

I removed the rear carpet and plastics to better pinpoint the noise... It appears to be coming from the drives side spring perch. If I put my hand on the wheel well on the inside, I can feel the noise in the metal.

 

Oh thats very very not good... I hate to bring bad news but it sounds like the support mount has torn or busted from the outer body shell where it comes from the underbody pan about 3/4 the way up behind the driver side seat. I used to have the same noise on my 90 Bird and after ripping all the interior out I found it. Here is a pic, you should check this brace. If its torn or busted free, you can try and weld it back, but its a real pita cause the center body pan pulls up once that is free, and you have to jack up the outer body shell to get that brace back close enough to weld it back. And dont plan on it lasting forever, there is a lot of stress on that joint and once the body seam along the floor pan and body panel gets rusted out, all the stress is placed on that one brace. I have over 100 lbs of weld on my 90 Bird. I ended up having to weld in frame rails front to back on both sides cause the rear control arms simply rusted and busted free. If your car is getting these kinds of damages, then I seriously suggest you get rid of it asap, cause it never gets better.

Without the rear seats or carpet if you drive down the road and set up a vid camera at the area of the body seam on driver side where the seat back is, and then watch it, if the center body pan moves without the outer body shell then you definitely have the problem I just mentioned. i may have a pic or two of what I'm talking about from when I had the problem, let me look.

 

pics

 

Thanks for teh reply man.

Thankfully, I already checked that seam, and it is good! That's the seam I was most worried about first when the noise got bad. I had a parts firebird with that seam broken, no good! Maybe i'll weld it anyway Spot welds can use some improvement. My car is in great shape for the most part... it is pretty much rust free on the body. I am very stumped as to the cause of the noise though!

 

After mine ripped apart, and I welded it, I also welded in some braces in the back over where the spring perch is:

 

Ok, changed a lot of bushings and the springs (ws6 ya!)

The springs raised the car almost 2 inches over the tired old berli springs.

The noise is also resolved, it was a sway bar bushing!, not end link.. The most obvious thing and I dismissed it outright!

 

I got the swaybar and poly bushings installed.

It drives like a completely new car. I don't even know to to describe it. Next step, exhaust and new struts.

 

so i had the same thunk after lowering springs new shocks, new suspension components Yes i know this thread is 6 years old and im sure everyone has a solution by now, but should anyone else find this thread with the same problem, check the bracket that the sway bar link mounts to. Mine was loose and after way too long on my back tightening bolts i finally found it. Tightened that up and problem solved.

 

I have the exact same problem. I replaced the shocks a month ago, hearing this thunk, mostly at low speeds over bumps, from right rear (I think). Looked at the shocks and nothing seemed loose.

But the consensus on this thread is that if you haven't lowered your car, it's most likely loose bolts on the shocks or sway bar. So I put the car up on jack stands and got out the torque wrench. But I didn't have to look far.

The rubber on the top of the sway bar bushing is completely gone. You can see a little bit of blue plastic showing, where there used to be a big rubber cushion. Replacement part is $3 from Rock Auto. Should be an easy fix.