I believe you have two issues going on. The timing of the shifts is controlled by the bowden cable. Adjusting it will adjust the timing of the shifts. The harshness of the shifts is controlled by vacuum. More vacuum, less harsh shifts. Sounds like your transmission is getting too little vacuum. You'll need to monitor the amount of vacuum going to the modulator as your drive around and shift using a Mity Vac or vacuum gauge
t'd into the modulator line, led out of the cowl and resting on the windshield so you can see the vacuum levels.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13