#gearbox__gear_case  the shell (metal casing) in which a train of gears is sealed
  supertype:  shell.housing__case__casing  the housing or outer covering of something; "the clock has a walnut case"
  part:  transmission_shaft
  part of:  transmission_system__transmission  the gears that transmit power from an automobile engine via the driveshaft to the live axle
     part of:  drive_line_system__drive_line__driveline  mechanism that transmits power from the engine to the driving wheels of a motor vehicle
        part of:  motor_vehicle__motorvehicle__automotive_vehicle  a self-propelled wheeled vehicle that does not run on rails

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