Chevrolet: 2004 Impala noise, nissan maxima, buick regal

Question
I have a 2004 Impala with 34,000 miles & never wrecked. It has developed a noise which I can only describe as sounding like a loose full size spare tire in the trunk behind the rear seat of a mid 60's sedan.

It occurs when sometimes going over a pavement irregularity above 30 mph. The sounds seems to come from the area under the front of the console and right front floor board. I have had it at the dealer twice in the last month to no avail. It has never had a lose trim panel sqeak, it seems to come from underneath the floorboard. Have their been any issues with scrunching sounds where the front engine and suspension Aluminum cradle is attached to the unibody?  

Answer
The quick answer is: Its a GM "quality" vehicle. My 96 Buick Regal and 97 GTP all developed creaks, moans, and groans at around the 30,000 mile mark. My '98 Nissan Maxima has 100K on it and is as tight as a drum.

I would take it to Midas or equivalent suspension shop in the states for a free estimate. Could be a bad bushing or shock. More often than not they won't find anything wrong.

Its a GM...they make noise unfortunately.