Completely unplug the vacuum line from the transmission. It should shift ultra firm with no vacuum, that would also be my assumption from a leaking modulator. Change your fluid and filter before going crazy....if that doesn't solve it plus the vacuum unplugged, then I would move on to the springs in the valve body and/or worn clutches.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth