Last week out of nowhere i started hearing this odd rattling noise or crunchy noise from the rear of the car when under load at low rpms. Its definitely not the suspension from what i can tell. so that narrows it down to exhaust or rear drivetrain. however if it was drive train i think i would be hearing the noise more frequently and it would be getting worse. (i've blew up rear ends before and know when they start making noise its a time bomb)

anyway, the noise again only occurs under load at low rpms. like leaving from a stop light or accelerating in 3rd at 1500 rpms or so.

I've heard of other guys having problems with their flowmasters having baffles come loose and rattle. however i've never had this issue and have no idea if this is the same sound.

i've tapped on both mufflers and can't hear anything nor do i hear the sound just free revving. only under load (when drone is most present).

anybody else have any ideas.

 

maybe some one can rev it a few times while you stand out back and listen. Or maybe have them pull away while you listen. Heck jump in the trunk and have them pull away.
Does it make the noise every time? Jack it up and give the wheel a spin and listen

 

When I installed my GTAs, I had a odd rattling/vibration noise around 1200RPM under load...turns out it was the driver's side exhaust tip contacting the rear fascia! I installed some washers as spacers and the sound never occurred again.

 

My guess would be some part of the exhaust has moved a little and is now hitting something ...

 

Also, check the heat shields. They seem to be a frequent source of crunching and ratttling noises.