The present invention provides a leveling control system for a forestry machine (10) employing position sensors that relay information about the orientation of the carriage (12) in relation to the swing-house assembly (14) in order to control roll and pitch in a manner that maximizes the operating envelop of the leveling mechanism (38). The angles of pitch and roll of the swing-house assembly (14) in relation to the carriage (12) are measured and/or calculated and a controller (24) limits operation of the leveling mechanism (38) to an operating envelop that may be described in terms of pitch and droll. The cylinders (54, 56) are decelerated gradually as the operating envelop is approached. The controller (24) can include an automatic leveling mode. The controller (24) can change the function of the fore, aft, left and right operator controls so that they are true from the operator's frame of reference regardless of the rotary position of the cab relative to the carriage (12).