This might not answer your question directly, but should add fuel for the thought-fire: When it comes to vacuum modulated shifting, the lower the vacuum getting to the modulator, the harsher it shifts--tends to shift later also. Try cutting an opening in the vacuum hose where it will lose partial vacuum--when it shifts, it'll prolly be late and harsh. When downshifting, it will prolly bang into the lower gear(s) too. Go figure? Try adjusting the throttle pressure cable (near where it & the accelerator cable go thru their "square" holes in their support brackets). I THINK the proper way is to depress the metal friction-holder inside the cable housing, an oval-shaped flat metallic object just the right size to get your thumb onto--it has a tiny hole right where your depressing finger fits-- & allow the housing with the "rounded" end (thru which the cable exits on its way to fasten to the throttle assy) to slide backwards, toward tranny. Now, pull the throttle assy WIDE OPEN, all the while keeping friction off the cable, allowing the now extended cable to pull its housing the last cms. of movement. Release the metal friction holder to maintain this position. It should now be self-adjusted. Often makes quite a difference in the shift pattern. HTH & good luck. Please let us know what did and did not work. Regards.............s (GOSH, I HOPE THIS WORKS. WOULDN'T THAT BE SOMETHING JUST SHORT OF GREAT?)