I was trying to find the torsional stiffness of a planetary gear stage manually. I was able to calculate the results by fixing ring and planet carrier. and giving torque at the sun shaft end. I am willing to know how would the results vary if the ring gear is fixed to a flexible housing and planet carrier is fixed.(I would like to know how the torsional stiffness of a planetary gear stage vary if all parts are set loose and the ring gear is set loose in DRESP.)