2003 Dodge Ram What could be wrong?

Check exhaust shields

I looked but I'm not exactly sure what it is I'm looking for. I felt a soft spot near the catalytic converter, and I saw that a plug end from the catalytic converter was touching the heat shield leaving a black mark I guess from it melting.

When exhaust cold
hit the exhaust with hand
listen for loose tin sounds

Ok I just checked the exhaust I only heard the vibration of the exhaust but it does not sound like the rattling noise I've been hearing. Nor did I hear any tin noises. I did put the exhaust on my self and the ubolts didn't close the pipes enough to keep the exhaust air from coming out. I tried to seal the pipes where they connect but I see black chalky stuff on the outside. Could that have had something to do with the noise? I don't want to say that the exhaust is not the problem so I'll wait to hear what you think. Back to the heatshield should I take them off to see if there's something wrong?

Use a metal wire and rap it around them tight easier
and quicker if that take care of the noise than you can remove the shield if you elect

I reread what First posted And I don't think I said what I needed to say. It is not a constant sound just a sudden sound of like a second or two. If I hold the gas at the right place i hear it longer but not as violent, but it doesn't always sound when I try to make the noise. I let my father drive it while I listened and it appeared to come from the middle to the back of the truck so It could be the heat shield and I missed it or something else. I did look at the heat shield but couldn't simulate the noise. A question I was hoping you could answer is if air is escaping the exhaust in the wrong places could that be what is causing the sound? Thanks BMRFIXIT for your help.

If have a leak in the exhaust system it would be at all time more noticeable when gas applied

I would suspect an exhaust shield or exhaust rattling and hitting something
if the sound ,sound like you have few small rocks in a tin can rooming around
its an exhaust