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Knocking sound coming from back of car

54K views 33 replies 14 participants last post by  Bill Brown 
#1 ·
Hey guys,

Well to make a long story short, there is this annoying as hell knocking sound that comes from the back of my car. It hear it every time I hit a bump.

So about a month and a half ago, I brought it to my mechanic and he said he checked every component in the back of my car to make sure every thing is tight and he said he doesn't know where this sound is coming from. At first he said it might be the "links" after checking them out they were fine.

So I then decided to bring it to another garage and over the phone he said that it might be my "plates". Something to do with suspension or shocks im not too sure what he said. i brought it in, he took if for a test drive and hear the sound. He lifts my car up and plates are fine. once again he checked for any loose parts and couldn't find anything.

I then decided to bring it into my GM dealer (last resort since i don't wanna pay outta my ass). They also cant find the problem.

I am freaking out, the sound is driving me crazy. Feels as if im driving a shit box....I don't know what to do or where to go. I have a 2005 G6 with 103,000 km.

Have any of u guys have had a similar problem?
 
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#2 ·
I haven't had this problem on my G6, but I had something similar on my Monte Carlo. Does it sound like it is rattling when you hit even the slightest bump?

For my Monte Carlo, it was bad strut bushings. The mechanic I go to, kept tightening them down but it did nothing. The whole sleeve was worn out. Not sure of the suspension set up in the G6, but might be something to look at.
 
#10 ·
It's the SWAY BAR BUSHINGS

I had this problem about a year ago. It almost sounded like a horse galoping down the road in the rear end. It took me awhile to figure it out. I had my wife rock the car side to side while I looked for the source of the noise. It was a LOUD knocking noise that almost seemed to come from the trunk area where it was amplified the most. Then I got underneath the back and just felt around for vibration only to find that my sway bar bushings were SO wore out that there was almost a half inch gap inside the bushings. I ordered the replacement parts, went to put em in and 3 out of the 4 bolt heads twisted off that holds the bushing bracket in place. (I was totally pissed by now :mad:). I ended up having to drill out the tiny bolts for the brackets and re-tapped the new threads and put Grade 8 replacement bolts in.:bash: It was a mess and total hassle to do this, BTW. After dropping the rear end subframe to get enough room to do anything, the new ones were installed, done. And now, she rides as good as new...:):bravo::D
 
#11 ·
Get under the car when its cold, and try to wiggle around the muffler, Maybe a hanger broke and it's tapping the trunk or bumper?

Also behind the rear bumper cover is a plastic energy absorber, maybe it was damaged or not installed properly and knocks around. If you reach up between the bumper and the muffler you can feel it. I would just just kind of grab it and move it around a bunch and see what it sounds like. I thought mine was squeaking real bad so I pulled it off and put some rubber strips in so it can barely move.
 
#13 ·
It's only when I drive over bumps. It's almost as if something is loose. to be honest I never got it fixed. 3 different mechanics said its not worth the money and to endure the sound.

All 3 have said its bushings but it could be in different locations. I'm actually going to sell my car this summer so I'm debating if I should fix it or leave it as is. Hope potential buyers won't get turned off by that sound...
 
#14 ·
Do this...

Start from here:
Jack the car up so that it's off the ground, starting with the front end. Wiggle each tire from side to side, left to right. If it is loose, it will make a clunking noise. If it does make the clunking sound or something similar, look on the inside at the ball joint(the joint with a rubber boot on the bottom-side of the hub). If the ball joint is bad, u will be able to see sloppy movement+reproduce the clunky sound that u hear by doing this. They are fairly easy to replace, but they can only be purchased with the whole control arm assembly(comes with new arm bushings too). It only takes 3 bolts to remove and install. Place a jack under the engine(using a piece of wood for cushion). Jack the engine up just enough to remove the lower engine mount. Remove it. Then unbolt the control arm (after disassembling the caliper, caliper bracket and axle nut, etc). Just ask if u have any questions.

Here's Advance Auto's links

Right side:
http://shop.advanceautoparts.com/we...-OE-Solutions_21299161-P_2071_R|GRP60005_____

Left side:

http://shop.advanceautoparts.com/we...-OE-Solutions_21299160-P_2071_R|GRP60005_____
 
#15 ·
Start from here:
Jack the car up so that it's off the ground, starting with the front end. Wiggle each tire from side to side, left to right. If it is loose, it will make a clunking noise. If it does make the clunking sound or something similar, look on the inside at the ball joint(the joint with a rubber boot on the bottom-side of the hub). If the ball joint is bad, u will be able to see sloppy movement+reproduce the clunky sound that u hear by doing this. They are fairly easy to replace, but they can only be purchased with the whole control arm assembly(comes with new arm bushings too). It only takes 3 bolts to remove and install. Place a jack under the engine(using a piece of wood for cushion). Jack the engine up just enough to remove the lower engine mount. Remove it. Then unbolt the control arm (after disassembling the caliper, caliper bracket and axle nut, etc). Just ask if u have any questions.

Here's Advance Auto's links

Right side:
http://shop.advanceautoparts.com/we...-OE-Solutions_21299161-P_2071_R|GRP60005_____

Left side:

http://shop.advanceautoparts.com/we...-OE-Solutions_21299160-P_2071_R|GRP60005_____

The sound is coming from the back of my car. The front is ok. I wish I could record the sound to make you guys hear it. It's as if there is something loose. Those mechanics seem to think its worn out bushings. However they said it could e in several places.

Is there any way for me to check those bushings without removing any parts?? Where and what do I look for?
 
#16 ·
Ok. I had this prob on my GTP. Have someone rock the car side to side. Crawl underneath the back and put ur hand on the sway bar(away from any pinch spots). Can u feel the vibration of the clunk noise when u touch the sway bar? If u can, chances are that u have worn out sway bar bushings. Just follow the bar to each side to where it appears to have a bracket clamp with 2 bolts holding it. Your sway bar bushings should be in between the sway bar and the bracket clamp on each side directly under the trunk/seat area(underneath, bolted to the rear subframe). Just ask if u have questions.
 
#18 ·
I have the same problem,dealership told me it was the shocks. I replaced a number of things on the car, struts, shocks, brakes on all four corners, front sway bar links, inner outter tie rods, and front sway bar bushings, took car for test drive, front was nice and tight/solid (big improvement) still clunking in the rear though. took it in for the alignment, no go, need front ball joint, but they did notice the rear sway bar bushing is totally worn along with the link. this is very common cause of clunking noises from the rear on g6's
 
#21 ·
had a clunking about a year ago shortly after having a flat and buying 4 new tires, turned out to be the tire shop put the spare in wrong. this time when a similar noise came around, the first thing i did was take the spare out and took it for a ride, still had clunk, figured I would at least get it aligned since I just installed struts and the tie rods, alignment guy also noticed a bad front ball joint (i thought it might be questionable but didn't want to fork out the dough when doing the tie rods and struts) and the sway bar bushing in rear was bad and had slop along with the link being worn, gm parts direct has the whole kit and kaboodle for $70.78, everywhere else i've looked just have the link for 50-60 and the bushing for around 10,I like to go oem when i can unless it's a cheaper and proven upgrade (made it 140,000 on oem). anyone know of a cheaper proven upgrade?
 
#26 ·
I had an extremely similar issue on mine, it happened to be the that the jack and wrench for the spare were not put in right and clunking around in the back. I know you said you checked already but you may want to take the spare and tools out of the trunk and drive around and see if the sound is gone after that.
 
#28 ·
I have the same problem, it sounds REALLY bad. Makes the car sound so unstable. I had a front clunk, but turned out it went away when I installed my eibachs and new struts/mounts. As for the back, my mechanic told me it was the bushing inside the shock where it mounts, so I went ahead and replaced the shocks; still there. Ill have to check out the rear sway, but I'm in the same boat you are! It sucks!s
 
#29 ·
It has to be something in the suspension. Bushings, links, sway bar, maybe your fuel tank is lose, try and check for that. Are your tires aligned? maybe your need an alignment in general. Could be a couple of things. My mothers acura tl had a rear knocking sound and it was coming from the tire, we didn't know til one day it just exploded on the e-way and after replacing it and getting the wheel aligned, the knocking sounds went away.
 
#32 ·
I'm glad I stumbled upon this thread. By the sounds of things, rear sway bar bushings is whats wrong with my car too.
 
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