Vibrating metal noise - exhaust?

[Kmvreter]

Got a new noise that just started today. Haven't seen anything like this mentioned on the forum.

It's a sheet metal rattle from the rear. It's not consistent, either in frequency or volume. Comes and goes. I'm thinking something loose on the exhaust but it's not always there. I thought we had a robust stainless exhaust system that doesn't rot so I can't seem to figure it out. I've had a similar noise on a fomer ride. That was more consistent because it was a broken baffle in a cheap muffler.
I don't have time to crawl around and look for the source right now. Any ideas?

 

[Kmvreter]

Found it.
The underbody heat shield above the muffler has corroded through at the rear mounting points. It's partially resting on the muffler. The shield appears to be a thin gauge aluminized metal and is held up in place by washer type nuts on a bolt or stud. The shield has worn through the nut pattern. Time to get some stainless fender washers and nuts to reattach it.
Any one else come across this?

 

[Kmvreter]

The noise got worse. Turns out all 4 mounting points have broken loose and the shield is just flapping around. This sped up the need to fix even though this is lousy weather to be crawling around under the truck. Got 2 points reattached with a stainless fender washer, lock washer and nut. Sorry there aren't any pics but I'll try to get some when I go to do the other hard to reach points in better weather.

 

[Tego]

I was having the exact same issue, I thought it was my tranny going on me...lol! I ripped off the heatshield at my work parking lot.

 

[k2damfc]

I'm having the exact sound too. But I've checked shields and nothing is loose. It almost seems like I'm losing power too. Only happens at first stage of gears, 1000-2000 rpms then goes back to quiet and more power. I also got a thrown p0420 code once then went away by itself. I'm almost thinking my cat has gone bad due to misfiring from a bad injector. But I have no clue and not sure where to even start. She still runs and still climbs but it does get annoying wheeling when I'm never really getting more then 3k rpms most the time. Not sure if it's related but every once in a while it seems that after sitting at a light or sign for a sec and I punch it, it kinda stalls slightly then picks right back up. Currently reading no codes at all.

Sorry for thread hijacking. Only way I can throw out my questions. I've done some research here and it ends up people just talking shyte on eachother for replaceing cats when they should of started with 02 sensors, just gettin old reading thru all that.