I don't think you have any kind of vacuum issue. From what I've read, vacuum is set up to soften the shift on these transmissions. Usually the symptom of a vacuum problem is harsh shifting.

Maybe a possible B2 piston problem? Although, this usually is a sudden catastrophic failure in forward gears, with reverse working normally.

The shop will probably need to put pressure gauges on the transmission to see if there is a pump issue.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )