My '87 300d downshifts with a clunk under a certain condition. It happens when I get off the highway and slow from 50 mph or so to 20 to 25 mph briefly to cruise through the tollbooth with my electronic pass. After I coast through the tollbooth, the car downshifts with a clunk even when I only give it moderate pedal (about halfway down or less). I have watched the rpms and am usually turning about 2000 when I hit the pedal. If I feather the pedal until I get to about 2500, I don't get the clunk. Here's what I've tried so far:
1. Adjusted Vacuum Control Valve (VCV) according to manual.
2. Cranked adjustment on Vacuum Amplifier fully clockwise (for max. vacuum)
Test drove and still got the clunk, so:
3. Adjusted VCV fully clockwise, still got the clunk
4. Adjusted VCV fully counterclockwise, still got the clunk
5. Teed into VCV and checked at idle, 10 inHg
6. Teed into Vacuum Amp output to tranny and test drove, 13 inHg at idle (I believe that Steve Brotherton's article http://www.continentalimports.com/ser_ic20242.html specifies 15-17 should be going to the modulator)
7. Vac tested modulator with mityvac and it held vac for about 20 mins perfectly.

I have not touched the modulator on the transmission. My other symptom is that the car jerks back when put into R and forward when put into D. I have heard this is normal, but I have my doubts. To this point I have not adjusted my throttle linkage, my bowden cable, or the little two piece slide with an adjustment which I read about on mbz.org http://www.mercedesdismantlers.com/722.3and722.416_transmission_adjustments.html. Is the clunky downshift normal? Is the jerky shift out of neutral normal? Should I first adjust the throttle linkage even though the car seems to have good power and the shift points seem fine?

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87 300D 162,000 miles: It's not just a car, it's an adventure!