I found the problem!!! Its the rear stabilizer bar bushing. Its cracked. Check it. Its a pain in the *** to remove, but $40.00 later, never heard it again!!!

 

glad to hear YOU found YOUR issue.

 

I attached a link to show the part I replaced. After having the car checked out at different mechanics, and spent a couple thousand, this little part caused me to nearly go insane. The one shown is superior to the OEM. I hope this helps someone.

http://shop.advanceautoparts.com/p/m...+bar+bushings#

Another sound I had a problem with before that was a constant "whirring" sound coming from the back of the car, that slowly got louder over time. It was a warped axle. The car used too much torque when ever I peeled out (cuz of my lead foot) and slightly bent it, Had to replace. See, I had a custom exhaust put on and between that and my stereo, never really noticed it until I started feeling a slight vibration when coasting. Again, I hope it helps someone.

 

 

I have the same sound and it's driving me crazy! I just replaced the rear shocks (KYB) on both sides, and I can still hear the noise when I go over a bumpy road or take a turn. My mechanic removed everything in the trunk and rear, but could not figure out what it was. He said nothing is loose and everything is in place. He said he gave up...
Sigh...any suggestions?

 

Update: problem solved! The noise is gone! A user named Blue Dream in this forum was right. In another thread he said, "sedans have a grey X brace behind the rear seats. Over time the bolts holding it tight can loosen and cause the same sound you're describing. The fix is relatively simple, remove the rear seat backs, tighten the bolts with a little Loctite, and put the seats back."