A drive train for driving a working unit of a self-propelled harvester is disclosed. The drive train includes a selectable belt drive with a drive belt, which operationally combines a drive belt pulley and an output belt pulley. The output belt pulley of the belt drive is operationally connected to the working unit via a drive shaft. The drive train comprises a clutch system, combining the functions of a belt clutch and an overload clutch into a single construction unit, with the response characteristic of the overload clutch system being hydraulically adjustable.