What is W123 proper tranny operation?
 

All, I'm new to my old 1980 300cd. Since I've had it, the automatic transmission has operated like more of a manual transmission, where the shift is instigated by backing off the accelerator. Now, I parked the thing back in July, and just started driving it again. The transmission operates in the same manner, only more pronounced. That is, it refuses to shift (ever) unless you ease off the gas. Further, when transitioning from first to second, the car seems to pause in neutral before finally hitting second. This delayed 1-2 shift problem was nonexistent before it was parked. I understand the vacuum system plays a role in the tranny operation, so I will mention having problems with the vacuum portion of my trunk lock operation arising during the same time period. I also understand it is possible to adjust a kickdown switch, though my repair CD inexplicably doesn't cover actually adjusting it. Additionally, the transmission was supposedly rebuilt perhaps 3000 miles ago, though I was not the owner at the time. What is the likely culprit here? Thanks.