Here's a good one for you...a bad vent vacuum actuator is causing a hard shift.

[240Joe]

I've been working on my 83 300D and am down to trying to soften up the 1st to 2nd gear shift. I put the vacuum gauge on the line to the tranny, and everything appeared normal.

Today, I made the measurement again, and at idle I'm only seeing 10 in of hg. I know that in the past it was always about 15 in of hg at idle. After a few minutes of pulling and pluging lines, I found that the vacuum line to the climate control unit was the cause, but only when the control unit was set to vent. If it was turned off, the vacuum jumped back up to 15 inches of hg.

The cause is another bad vacuum actuator (I found another one last week).

So I put it all back together and took it for a test drive. When the climate control was set to off, the shifts were still sharp, but overall very nice. Then I hit the vent button, and the 1st to 2nd gear shift was again very, very abupt...way too harsh.

I guess the moral of the story is that when vacuum is used to simulate a gas engine for the transmission modulator, and that vacuum runs to many places, make sure when you're troubleshooting you measure the vacuum with all of the climate control settings the same as when you note the problem (either that or plug the line going to the climate control while troubleshooting)

Joe