My dryer is making a clicking sound like a coin is loose and tumbling but nothing is inside?

I like working on dryers, they are light as far as being able to put it on what ever side you want. drag it so you can access the back and dig into the vent area. You know it's in the vents, go for it , doesn't need many tools either. I would sneak a peak at the drum belt it may have a piece missing and that is what you are hearing.