Abstract: An overload release clutch mechanism which includes a housing member and a rotor member mounted for relative rotation and means associated with said members for effecting transmission of rotary movement from one of said members to the other end being effective to disengage said members upon the application of a torque exceeding a predetermined value to one of said members is equipped with means operative at any time during the operating cycle of the mechanism to vary the torque level at which disengagement occurs. The members are held in engagement to transmit such rotary movement by fluid under pressure and the means operative to vary the torque level at which disengagement occurs control the pressure of said fluid.