Rear suspension noise, 500E

[benzmark]

Question for 124 chassis experts, specifically 500E. I have a 93 500
e with 44,000 miles with an annoying rattle in the right rear suspension which I cannot locate. Have changed the sway bar link, the air cell, the hydropneumatic strut(last resort) and I have tightened all of the suspension links. All of the bushings look and feel tight as one would expect in this low mileage car. The half shafts feel tight, without any suspect clunking noise. The noise only appears at speeds under 40mph and is somewhat intermittent and only when going over bumps in pavement. One local shop I had look at the car reported that the noise did not occur in reverse. Quite frustrating. Any ideas?