Abstract: An automatically compliant self-adjusting geared transmission mechanism is described that involves no controls of any kind and provides a range of stepless variation in the ratio of its output-torque to its input-torque together with the inversely corresponding variation in output to input rotary-speed ratio. The transmission mechanism comprises coaxial rotatably supported adjacent input and output shafts, each carrying a sun-gear fixedly mounted on its mutually proximate end. The sun-gears mesh with corresponding planetary gears of a planetary gear-spool rotatably mounted on a rotor which is itself freely rotatable about the sun-gears' axis. The proportions of the gear diameters are designed so as to develop a torque in the rotor that balances its torque reaction to the output-torque of the gear-train, while coincidentally providing essential variability to the output to input rotary-speed ratio.