So, I've developed a transmission issue in Goldbug. Goldbug is a 1985 300D chassis (California emissions) with a 1983 300SD engine (not California emissions). The transmission is the original one from the 1985, California emissions (which is apparently different than that for non-California emissions for the 1985 model year). When I reassembled the engine with the transmission, two things of note happened/occurred:
1) I replaced the black modulator valve of the California emissions with the Green on for the federal emissions, because I figured that the engine was now effectively a Federal emissions car. This info is included for completeness.
2) I broke the front hydraulic pump, which then had to be replaced with a used one, after I sought professional help.

Car drove away well from the mechanic's place, albeit with a cloud of smoke which resolved with a valve adjustment, rebuilt injectors, new fuel filters and draining the fuel tank.

So, I proudly drove Goldbug over to take its Arizona emissions test, which measures opacity of the exhaust. She passed with flying colors, scoring a 1.1%, with 30% passing. Hooray!

On the way back unfortunately (don't these posts always have this particular inflection point?), I stopped at a light. Car was driving great. Light turns green. I push down pedal. Car moves ahead, only slowly. Then car doesn't upshift. I manage to get across intersection, pull over, check transmission fluid, have to back up (which works fine, no problem), so I take off again. Car generally behaves as if transmission on last legs, maximum speed about 25 mph. A couple times, it seems to imperceptible upshift, allowing me to gradually accelerate to 40-45 mph, although I did not perceive upshift. I straggle home, park car in driveway and use other car for transport.

Next day, I start car, no forward gears, but reverse works fine, strong, no problem.

Any thoughts from anyone regarding problem, and also protocol to round up the ususal suspects, before I resort to professional help? Little thing or big bad dead transmission thing? In the words of Ben Stein in "Ferris Bueller's Day Off," "Anyone? Anyone?"

__________________
Der Panzermann und Fraulein Fahrvergnuegen

1991 420SEL 201K "The Big Blue One"
1985 300DT 205K chassis/285K engine nee California emissions "Goldbug"
1983 300TDT 255K "The Womble"
1983 300 DT 214K "Sea Sprite"-Rear-ended a truck
1983 300SD 285K "The Donor" Gave his life so that others can live
1980 500SL Euro 105K "Der Panzer"