My father(a retired transmission man) says it sounds like you aren't getting enough pressure from the pump. There is also a pressure regulator valve in the valve body that might be hung up. He said that to adjust the bands properly, you tighten the band(loosely - not snug by any means) and then back the adjuster off 2 - 2 1/2 turns, and tighten the locking nut. His main thought was that it needed a new pump, but that the valve may be hung up, or even one of the valve body gaskets might be in wrong. I hope this helps.
