A transmission for use with a powered surgical tool, the tool having a body and a rotating drive spindle that extends from the body configured to releasably receive and drive a cutting implement, said transmission comprising: a housing (382, 412), the housing having: at least one feature (418, 419) for releasably attaching the housing to the tool body; and at least one feature (385, 387) for releasably attaching a pump cassette to the housing; a drive link disposed in the housing (382, 412) for reciprocating movement in the housing, the drive link including a feature for engaging a driven component of the pump cassette attached to the housing (382, 412); and a gear train internal to the housing (382, 412), the gear train including an input shaft for engaging the tool drive spindle; wherein the gear train is connected to the drive link and is adapted to convert the rotary motion of the input shaft into motion that reciprocates the drive link; characterized in that: the housing (382, 412) is shaped to have: a head, said head being shaped to be coupled to a distal end of the tool, and an arm that extends proximally from the head, said arm being positioned to extend over an outer surface of the tool body, said arm having a top surface with an opening, the top surface adapted to receive the pump cassette so that the pump cassette extends over the tool body; a plurality of features (385, 387, 402, 404) are attached to the housing (382, 412) for releasably holding the pump cassette to the top surface of said arm; the input shaft of the gear train is rotatably mounted in said head of the housing (382, 412); and the drive link is disposed in the housing so as to be disposed for reciprocating movement in said arm so that the drive link extends over the body and the feature for engaging the driven component of the pump cassette is accessible through the opening in the top surface of said arm. a housing (382, 412), the housing having: at least one feature (418, 419) for releasably attaching the housing to the tool body; and at least one feature (385, 387) for releasably attaching a pump cassette to the housing; a drive link disposed in the housing (382, 412) for reciprocating movement in the housing, the drive link including a feature for engaging a driven component of the pump cassette attached to the housing (382, 412); and a gear train internal to the housing (382, 412), the gear train including an input shaft for engaging the tool drive spindle; wherein the gear train is connected to the drive link and is adapted to convert the rotary motion of the input shaft into motion that reciprocates the drive link; characterized in that: the housing (382, 412) is shaped to have: a head, said head being shaped to be coupled to a distal end of the tool, and an arm that extends proximally from the head, said arm being positioned to extend over an outer surface of the tool body, said arm having a top surface with an opening, the top surface adapted to receive the pump cassette so that the pump cassette extends over the tool body; a plurality of features (385, 387, 402, 404) are attached to the housing (382, 412) for releasably holding the pump cassette to the top surface of said arm; the input shaft of the gear train is rotatably mounted in said head of the housing (382, 412); and the drive link is disposed in the housing so as to be disposed for reciprocating movement in said arm so that the drive link extends over the body and the feature for engaging the driven component of the pump cassette is accessible through the opening in the top surface of said arm. the housing (382, 412) is shaped to have: a head, said head being shaped to be coupled to a distal end of the tool, and an arm that extends proximally from the head, said arm being positioned to extend over an outer surface of the tool body, said arm having a top surface with an opening, the top surface adapted to receive the pump cassette so that the pump cassette extends over the tool body; a head, said head being shaped to be coupled to a distal end of the tool, and an arm that extends proximally from the head, said arm being positioned to extend over an outer surface of the tool body, said arm having a top surface with an opening, the top surface adapted to receive the pump cassette so that the pump cassette extends over the tool body; a plurality of features (385, 387, 402, 404) are attached to the housing (382, 412) for releasably holding the pump cassette to the top surface of said arm; the input shaft of the gear train is rotatably mounted in said head of the housing (382, 412); and the drive link is disposed in the housing so as to be disposed for reciprocating movement in said arm so that the drive link extends over the body and the feature for engaging the driven component of the pump cassette is accessible through the opening in the top surface of said arm.