rattle in the rear

[Kazimodo]

Hello , my 2007 hatchback started making rattling sounds from the rear ,
it has done that before , usually the heat shield so I went under and solidified it for the xx time , but the sound is still there ...
only when I start to roll and low speed < 5 mph.
I removed rear drums , there is a lip around the back plate , pretty rusty ,
so I pulled away all the loose rusty parts , put on new brake pads in rear ,
I still hear the rattle , like cracking frame , I grabbed at everything under and could not find any loose item explaining rattle .
anyone ever had that kind of sound ???
wheel bearing??
coil spring parts ??
parts inside muffler coming apart ??
200,000 km

thank for any kind of reply .