[Fox_]

Sometimes shifts are smooth and firm, sometimes it slams the out of it. Downshifts, 3 to 4, are harsh sometimes too.

No pattern, no consistency.

What I've done:

Replaced the vacuum line that runs from engine to regulator
Checked the vacuum while running, tee'd in a mityvac, normal.
Changed the fluid/filter.
Adjusted the regulator.

Now it's starting to get hesitant on the upshifts.

Low RPM shifts and WOT shifts are fine, normal driving shifts suck.

[Schocki]

Check the vacuum regulator itself. You can replace it with a new upgraded MB unit. Roger should have them.

https://www.youtube.com/watch?v=gM4KZvwsCW0

[Fox_]

Modulator holds a vacuum well, beyond that I don't know.

I'll look at it. Thanks.

[Landseer]

Sometimes the little rubber cap that covers the adjustment mechanism develops cracks.