Thunk in rear

[WeeYari]

I think I've seen thread(s) on this before but can't find anything. My car has developed a persistent thunk in the rear that is driving me absolutely bonkers.

I've removed absolutely everything from the back, inspected the suspension, exhaust hangers, seat mounts, and whatever else in, around, or under the car I can see and touch.

Thought I found it when I noticed the axle-back exhaust gasket was shot and maybe the flanges where banging together. Nope.

Again thought I found it when I discovered that two foam rubber cushions under the spare tire had dislodged and maybe the wheel was bumping against the floor pan. Nope.

I can't go over the smallest of bumps without a thunk. Washboard road surfaces, it becomes absolutely crazy.

Any ideas at all????