I think that the list above covers it all really!

however, Most of those items may be perfectly fine, and just one or two are causing the problem. Broken springs are a good possibility and easy to spot...

Best bet would be just to check and test as many of those points as is possible.

Play and excess movement in ball-joints and bushes is reasonably easy to spot, and as your issue is SO bad, the faulty parts should stand out like a sore thumb!

I'm betting that the shocks on the rear are pretty toasted and or their bushes.
--Bottom ball-joints can cause wandering at speed on good flat roads, bushes on TCA can cause Horrible tyre wear. Steering knuckles can cause all sorts of vague steering feelings and clunks and the idler bush can cause some odd knocking noises when rocking steering...

Rear trailing arm bushes are pretty solid, but at 25 odd years old should be given a careful check...

Steering-box may have some wear, but careful adjustment can improve things no end--I had a steering on one W123 so 'loose', you could turn steering-wheel 6" before anything happened, Careful adjustement brought this right down and transformed the car!--Saved a HUGE packet too!

(Adjustment is on the top of steering-box, Large lock-nut, 19mm? and Allen key 7mm? Screw Allen-bolt Outwards to reduce the the amount of play, and settle for a 'loose movement' at the edge of the steering-wheel of about 1/2 inch, with NO tightness, do adjustment with wheels in dead ahead position and without engine running....)

__________________
http://i190.photobucket.com/albums/z...0TDnoplate.jpg

Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....