I have a 2003 Dodge Stratus, automatic, 4 cyl, 4 door with 203,000 miles.

​​​​​​I have noticed in the passenger rear area, the car wobbles, it sounds like something is loose and shaking around in the car. The tires have recently been balanced, rotors are fine, etc but it has happened for quite some time, even before the rear struts were replaced, but the wobbling is localized to the right rear side of the vehicle. At high speeds it seems to unbalance the car and cause the rest of it to shake. It feels like an up-and-down type of wobbling.

Anyone have any ideas?