A coupling system including a sun gear coupling (32) and a ring gear coupling (158) for connecting the sun gear(36) and the ring gear housing (50) of a planetary gear train (26) to an external shaft (24) and an external mechanical ground (56) respectively are each characterized by undulant cross sections for accommodating parallel and angular misalignments. A ring gear deflection limiter (158), antirotation spline (190) and vibration damper are also included for enhanced operation.
