On the older models there is a lever on the sway bar that connects to the control valve with a link that has a threaded portion between to ball and socket ends. Should be in the middle of the say bar. This is the height control: unlock the nut at each end and turn the rod to make it longer or shorter to adjust the height of the rear suspension. Don't turn it too far, support the car while adjusting, and don't forget to tighten the lock nut down when you are done!
If you can't find the adjustment or don't want to damage anything, and independent shop or dealer should be able to adjust the height for you with no problem.
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!