hard shifting when a/c on
 

I have recently purchased ( I will be the 3rd owner) a 1986 300sdl. I have owned a couple of VW deisels before. This car had 125,000 miles on it when I got it and was in near-showroom condition. Or so I thought. After about $2500 worth of mainatinence and parts replacements ( ALDA valve, A/C vacume elements, aspirator blower motor, bulbs, door switches, puddle lights, hood insulator, window switch, etc.) it is a sweet car and fits me just right. A little slow ( to be expected ) but better after the ALDA replacement. Now to the problem.
I have noticed that besides being noticeably more powerful with the A/C off, the tranny shifts like butter with the A/C off, but with it on, the shifts are hard. Any suggestions?

Sounds like you've got A/C vacuum control pods leaking. Thus causing a low vacuum condition affecting the transmission.