Rattle issue around rear bumper.

I have noticed when driving down secondary roads that have rough areas. The rear of the truck will rattle when I hit those rough spots. Thinking it is around the spare tire or tail pipe area. Have not taken time to look at it yet. Anybody experienced this issue? The only time I hear it is when I hit the rough spots. Thought at first it was the receiver hitch, but that is not it.

 

Is the spare tire fully wound up so it's snug in the frame? Last summer I was driving around and kept hearing a rattle, turns out it was the spare tire carrier. I had dropped the spare to clean and paint the frame and the metal piece that fits through the hub hole of the spare rattles like a bitch if there is no tension on it.

 

That is what it sounds like, going to check it maybe this coming weekend. Turned off cold an raining right now. Wait till it warms up some first.