I am having a rattle/ rumble noise under my car

What is your question?

I have a 2013 Grand Caravan that makes noise mainly on rough roads, but not on smooth roads. It is not the spare tire as I removed it completely to eliminate that, although that is what it sounds like. Something is loose somewhere, and we have 3 more in our rental fleet that makes the same noise but they are 2019 caravans. I just bought tis used and it only has 37000 mi.

What makes this problem better or worse?

Bumps make it worse

How long has your 2007 Dodge Caravan had this problem?

I bought it used in Oct.