My old 220D (very similar rear suspension) had both links completely missing. Handled very strangely until I found they were gone.
Check the two bushings that hold the sway bar to the bottom of the trunk, too. These can get old and hard, and allow the sway bar to thump around. Sounds like a full glass soda bottle fell over in the trunk, or something is rolling around.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!