Rattling like a tin can

I can hear this noise that sounds like a rattling tin can when I'm moving. It's coming from underneath, but I can't quite figure out where. At first I thought maybe it was the fragments in the Cat. but now I'm not so sure.
Any of you have any ideas?

Normally the cat's heat shield is the first thing to go. It makes a tinny rattle sound. I usually just yank them off when they start to rattle.

I ripped mine off too, then I replaced it not knowing if it would cause issues with passing inspection.

I can hear this noise that sounds like a rattling tin can when I'm moving. It's coming from underneath, but I can't quite figure out where. At first I thought maybe it was the fragments in the Cat. but now I'm not so sure.
Any of you have any ideas?

Well you need to craw under there and have a look around.
But be sure to put stands under it before getting under there.
And watch they cats they get hot.
Tail pipe rubbing or lose parts many things can rattle just look it over and pinpoint rattle.
As said heat shields and if the rattle is inside cat new cats is the answer.
MT