Replaced leaking (would not hold vacuum) transmission modulator in '82 300D. Is it permissible to set the modulator pressure with the rear wheels off the ground, or is it essential that the car be on the road for the adjustment? I made the initial adjustment with the car on jack stands, at 30 mph. The 1-2 shift is pretty hard, 2-3 is good, 3-4 is firm. The clunk during downshift (that I was hoping to eliminate) is still there, at least some of the time. The downshift clunk is most noticable when accelerator pressure is reduced soon after an upshift has occured. The new modulator holds vacuum and the remainder of the vacuum system checks okay. Any ideas or insight will be appreciated.