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Discussion Starter #1
Howdy -- every time I go over a bump I get a significant vibrating thumping noise coming from what seems to be the middle bottom of my 2003. I should note that the sound is more of a low freq thud as opposed to a high pitched rattle. In giving the muffler a good push and pull that doesn't seem to be this cause. Has anyone out there had this issue and fixed it by replacing, removing or tieing down the cat conv heat shield? Many thanks.
 

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The heat shield is awfully light to be making anything that could be accurately described as a "thump".

My best guess would be to look at the spare tire. If it's just a little loose, it can make odd squeaks and thumps. Other than the exhaust system, there's not really much that's likely to move around between the engine / transmission and the rear subframe. Other suspects would be the rear swaybar bushings (not fun to change out) or possibly tie rod links.
 

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Just pop up the little panel inside the rear hatch (on the plastic trim just in front of the bumper). Give the adjuster that's now exposed a turn (19mm, IIRC) and I'm betting your problem disappears. The lug wrench will work if you don't have a ratchet / socket handy.
 

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The heat shield is awfully light to be making anything that could be accurately described as a "thump".

My best guess would be to look at the spare tire. If it's just a little loose, it can make odd squeaks and thumps. Other than the exhaust system, there's not really much that's likely to move around between the engine / transmission and the rear subframe. Other suspects would be the rear swaybar bushings (not fun to change out) or possibly tie rod links.
When I bought my project 04 last year I could have sworn I needed all bushings in back replaced. The squeaks and thumps we’re bad. But yep, just the spare a bit loose.
 

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Discussion Starter #6
Bummer -- not the spare (took it off and drove around). With regard to the thumping I should not that going over a bump or rough patch of road theres a vibrating /stuttering factor. It's not the muffler as it is solid. Thanks for any other ideas!
 

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Could be any number of bushings, including those on the shocks, swaybars or links. It might help to sit in the back (maybe 3rd row) and have someone else drive the car over a rough road.
 

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Discussion Starter #8
I meant to say shuddering above not stuttering. Anyway ... in checking my repair invoices I see that we had the rear swaybars done in 2016 (and there has probably been only 15,000 miles put on the car) and we did the rear bushings 33,000 miles ago. So does that just leave shocks as the last remaining rear possibility? Other than driving and guessing - how does one truly determine if its' the shocks.? Thanks again.
 

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Troubleshooting something like this can be difficult, since you can't be looking at the suspension while it's in use (well, I wouldn't recommend it, anyway). ;-)

What I'll normally do is to aim for pot holes or bumps to see if I can induce the sound with a particular input on a particular wheel. That at least narrows it down a bit. I replaced my rear shocks when I had an odd noise in the "rear suspension", and found out that it was indeed a loose spare tire (but hey, at 200,000+ miles, it was due for shocks anyway).

I should add that replacing those rear sway bushings is a bear, and it's always possible that the tech who did the job didn't get them tightened down enough. I'd say you might be able to crawl under the rear suspension and push the body up and down a bit to see if you can see any unusual movement anywhere. You might be able to spot an obviously bad bushing in the shock, too (or see movement when you rock the car).
 
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