As you noted, the rod/spring assembly did come out after a encounter with a pair of vice grips (it appeared to be glued into the old modulator and took some force to remove). When I replaced it, it was as you said, exactly the same as the old one- incredibly hard and late shifts into 2,3 and no fourth. It actually shifts so hard (and has so much RPM momentum) that the tires "bark" when you go from 1st to 2nd. I have started to look at the article and it looks very juicy to me, having no other clue as to how to find out what is going on With my tranny. I want this tunnel of transmission issues to end. I should also mention that the flippers that close the vaccum valves on the top of the valve cover assembly, are fine (a past problem) and the fluid and filter are both fresh, and the fluid that came out looked fine (as it should). There is also no apperent total vaccum faliure, as the brakes and door locks and fuel shutoff are all working. The only thing that is out of whack is that the drivers side door lock has to be locked to shut off the car, and it has been like that for many years. If you have any other clues other than what is give in the article, I'd love to hear them, as I know no other way of finding out what is going on.
Thank You,
Justin O'Dea Bozeman, MT