Thank you for the details, Frank. However, I'm aware the transmission is a 4-speed but I've never known mine to start in second. I've heard mixed opinions whether the diesels are supposed to do it or not, but it seems it's normal as no one else has mentioned it. I've not mentioned a 3-4 shift because it's never been a problem nor has its behavior changed greatly through my adjustments.

I actually believe the transmission is operating more the way it should now than before my adjustments - engagement of the forward gears when it's cold isn't as much of a gamble as it was before, and each shift is more consistent. Will too muchvacuum with the Bowden cable at "0" (accelerator at rest) cause the 1st gear glitch? If higher vacuum = lower trans. pressure, might excess vacuum drop fluid pressure below the point that the B2 stays engaged? Maybe I should disconnect the switchover valve (supposed to just make all shifts hard?) to see if it still does it? Not saying that's a substitute for checking vacuum and line pressure, but a preliminary test.

Edit: upon more reading in other forums, some owners report a 2nd gear start with a drop to first upon even the slightest accelerator movement. This could be what I'm feeling, but it seems Mercedes calibrated the transmissions differently for gas vs. diesel, and even for which rear end gears were in the car.

I agree a sluggish B1 could cause what I'm feeling, because if 2nd gear is in play from a dead stop (which I hadn't yet considered) the problem isn't slipping in first, but indecision or delay between first and second.

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".