Great info, thanks for sharing!
Now, I may be a little late to the party... but one major item has been overlooked here. The transmission shift point (controlled by the control cable) and shift firmness (controlled by the vacuum signal) on the 1987-1993 300D are based ENTIRELY on throttle position. Why is this critical? Because if your engine power output is below normal (due to ALDA issues, or any of a dozen other reasons)... the tranny will shift like crap (often a late, high rpm, harsh shift). But there may be nothing at all wrong with the tranny, or springs, or anything else. Fix the engine power output, and the tranny problems may go away.
Also, make sure the VCV on the side of the injection pump is set correctly. This is not a "seat of the pants" adjustment, there is one proper setting, and you don't tweak it either way. (It can cause weird shift issues if this is mis-adjusted!) See the FSM for the official procedure (
click here), but basically you loosen the mounting bolts, have a helper press the pedal to the floor (or pull the throttle cable to WOT), gently rotate the VCV (from full CCW turn it CW) until resistance is felt, then tighten down the bolts. Often it ends up right in the middle of the adjustment range. This is the FIRST step in correcting diesel tranny issues. The second step is making 100% sure that all the Tecalan vacuum tubing is intact and not leaking, along with checking the rubber fittings. Replace anything that is cracked, brittle, soft, or otherwise questionable. Then you have to fix the engine power output, particularly the off-idle power (generally fixed with ALDA adjustment).
When everything is set correctly, the transmission shifts should be butter smooth cold or hot, at light or medium throttle, with zero flaring. At WOT (kickdown) the shifts should be firm, and should occur at 4800rpm for each up shift. My '87 tranny has 300kmi on it, with all the original "K" springs (no Superior kit needed), and it shifts perfectly. But I've also spent a lot of time getting the engine power delivery correct (0-60 in 10 seconds), setting the VCV to spec, and replacing every vacuum tube & rubber hose in sight.
It's a good idea to replace all of the old fossilized stuff.
Hope this helps!
