Thumping sound underneath

I am experiencing a thumping noise emanating from underneath my 84 944. I think i have narrowed the source down to the underneath the rear of the vehicle (driver side, i think). Wheel bearings all seem OK. The noise is somewhat random, usually occurs on the freeway speeds ranging from 50 to 80 Mph, but I have noticed it at much slower residential driving. There is seemingly no correlation to braking or clutch work. Ball joints/rear sway bar/???? Any help would be greatly appreciated. It is becoming a great annoyance.

have you hit any small children lately? lol!
um... just a thought, it might be your ebrake... the e-brakes on these cars are small drum brakes inside the rear rotors to keep the rotor from warping while you have the e-brake on. i noticed that when i pull the e-brake a wee bit while moving it'll thump. check your cv joints... if it's them, the thumps will usually be durring acceleration and deceleration no matter how small.
um... i hope this wasn't just a bunch of useles rambling...

Yeti, Thanks for the advice, no rambling what-so-ever. I actually thought at one time the problem could be orginating from the e-brake and i tried engaging it lightly when i noticed the thumps to see if it effected anything. Results were inconclusive. Can you advise how to further check the e-brake? And the CV joints? Most appreciated...

does it happen wen u shift into the next gear

i have a random thump in the front of my car and it scared the crap outta me because i thought something was about to fall off. turned out its just the strut insert getting stuck slightly and then letting go. try pushing on the back and see if you hear the same noise.