what can be rattling in right rear when driving any speed.

What is your question?

The rattle noise just started it is in the right rear a dull like rattle noise like something is lose or hitting something. It happen at any speed. I checked exhaust hangers Ok. I am stumped? it is a 2005 Subaru legacy non turbo. I didn't see any control arm bushing bad. is there any problem with frame brackets breaking? the rattle noise is like something hitting together at a fair fast rate. It kind of sounds like when exhaust header hits the frame. but I can not see that happening in the right rear there.

What makes this problem better or worse?

it stops rattling when you come to a stop starts as soon as you start driving

How long has your 2005 Subaru Legacy had this problem?

one week