Abstract: A variable ratio transmission system for coupling a load to a source of rotational power includes a selector shaft having a selector gear axially movable on a fork dolly by an actuator including a lead screw, and a control motor; an inclined cluster shaft having a plurality N of spur gears rotatably supported thereon for being selectively meshed with the selector gear, at least N-1 of the spur gears being variably coupled to the cluster shaft by a one-way clutch for rotation therewith; and a controller for activating the actuator while preventing substantial torque-loading of any of the spur gears unless that spur gear is substantially meshed with the selector gear, the controller comparing a set of operating conditions of the power source with a predetermined operating envelope, and activating the actuator for bringing the set of operating conditions within the operating envelope, the operating conditions including an input operating speed and a set point variable that can be throttle position, torque, power