Abstract: A replacement mechanism or servo assembly for applying a band to an input member of an automatic transmission includes a housing in which an apply piston is located and to which an apply pin is connected. The piston is sealably movable in the housing and includes a major piston member having a first distal reaction face and a minor piston member integral with the major piston and having a second distal reaction face. A pressure fluid distribution device applies a working fluid against both of the first distal reaction face and the second distal reaction face in order to move the piston with the resultant force of the pressures on both reaction faces and to cause the apply pin to move toward the band to compress the band about the input member with this resultant force. In a preferred embodiment, the housing further includes a pressure separator immovably disposed between the first distal reaction face and an adjacent second proximal face of the minor piston member.