The sound from the rear only occurs when I go over a speed hump/bump. It happens when shock is under compression and rebound.

It sounds just like the noise a drawbar will make, when you go over a bump when it fits kind of losely in the reciever of a class III hitch.

Noise is not from: hatchback, support joints, link bushings, drop links, frame bushings, anntenna motor, spare tire, tools, rear wiper tank, shock absorbers, parking brake.

Any ideas?

Exhaust?

Geoff,

Forgot to mention that but no, I installed new rear muffler and four new rubber hangers/supports. The pipe on the rear muffler that goes from the center muffler to the rear muffler which is a part of the rear muffler was very rusty.

Is there anything in the tailgate, that could be loose and make the rattling noise I have?

There's something mentioned in the factory service manual about some 124 wagons suffering from clattering noises from the rear seats. Try folding them down completely and see if the noises persist.

Drove with seat fold down and in upright position, no difference.

Removed the plastic cover that covers fuel filter, thought it might be rubbing, but no difference.

Thought hard covering of fuel hose was rubbing against steel hydraulic lines form the hydropnematic control unit thus causing noise so I re-routed, no difference.

Could the differential mount be causing noise?