I just wanted to follow up on this issue as I have corrected the problem without replaceing any major components, namely the transmission.

While I was having the shifting anomoly, the car's glow light began to signal that a glow plug(s) had gone bad (glow light wouldn't come on when key was turned and would come on after the car started). I decided to replace all 5 glow plugs. In doing so, I removed the intake manifold, injector spider lines, and all associated shift linkage (ball sockets etc) in this area. When putting everything back together, I took the time to lubricate all the throttle linkage ball/sockets. There is a part of the throttle linkage assembly where the boden cable conncts to (whick is on the passenger side on a 2.5DT) that seemed stuck. When actuated it would not return smoothly. I cleaned and lubricated this mechanism along with all the other throttle linkage ball/sockets and shifting retruned to what it had been.

So to return to my original post, the lesson learned is that in following the KISS principle, I should have looked at an even more basic mechanism (throttle linkage) prior to condeming the vacuum system or transmission altogether.

Mark

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1987 300DT 127K
1987 300TDT 283K (Sold)
1999 528iTa 75K
1991 300D 2.5T 214K - Dead Tranny
1984 300DT 375K (Sold)