An agricultural device (10) for controlled unloading of grain including an unloader conveyor (34) including an enclosed housing having an inlet end (32) including an opening for receiving grain, and an opposite outlet end including a discharge opening through which the grain can be discharged. An unloader conveyor element (36, 40) extends through the housing between the ends and operable for conveying the grain through the housing from the inlet end (32) and discharging the grain through the discharge opening. The unloader conveyor element (36, 40) includes a substantially vertical unloader conveyor segment (36) connected to a substantially horizontal unloader conveyor segment (40). An unloader drive (44) selectably operates a portion of the conveyor element (36, 40) associated with the substantially vertical unloader conveyor segment (36) in a disengaged mode in response to a sensed cumulative loading condition of the substantially vertical unloader conveyor segment (36) and the substantially horizontal unloader conveyor segment (40) exceeding a predetermined value.
