I have had the Magnaflow 16616 kit on my truck since may. Last weekend, as stupid as I could be, I bottomed out the truck crossing over a curb and sat the truck down on the frame momentarily. Luck would have it that I only hit and crushed the transmission crossmember a lil bit. Now I have the most annoying rattling sound that only happens at low RPM, while in gear, (idle, 750 RPMish) coming from the damn exhaust. Trick is, I don't know where. Not sure if I jarred one of the brackets loose and shook something loose inside the muffler. Once the truck is moving, no sound. I'm confused as I can be.

 

that would be a hanger. look for the telltale signs such as dangling exhaust tips. just go under the truck and start lightly wiggling the pipes.