An HVAC controller housing including a plurality of valves extending therein for directing airflow to a plurality of ducts is provided. The housing is of the type including a side port extending outwardly from the housing and in fluid communication with one of the ducts. A drive gear is provided on the housing to drive a plurality of driven gears disposed on the housing for driving the plurality of valves. The driven gears are responsive to the drive gear through a transmission member comprising an annular idling gear in meshing engagement with the drive gears and at least one of the driven gears. The annular idling gear is rotatably supported on the housing and encircles the side port for efficient torque transfer between the drive gear and the driven gears.