A torque converter comprises a stationary housing within which a rotatable impeller is mounted for driving a rotatable turbine. The bladed impeller is mounted on an engine driven input shaft, and the bladed turbine is mounted on an output shaft on the same axis as the input shaft. The impeller blades and turbine blades move through an annular oil-filled passage. A plurality of stator blades are disposed in the passage in spaced-apart radial arrangement around the axis of the shafts. Eah stator blade is divided into two sections, namely, a fixed forward section and an adjustably movable or pivotable rear section. Means are provided to pivot the rear sections of all of the stator blades simultaneously so as to vary the width of the flow channel between each pair of adjacent stator blades between fully opened and fully closed positions and any position therebetween to thereby control the amount of oil available for use by the impeller and turbine and thereby enable regulation of the power output of the torque converter. The movable rear section of each stator blade is provided with a stem which extends through a sealed opening in the stationary housing and enables pivotal adjustment of the rear section of the stator blade about the axis of the stem. The stem axes are parallel to the shaft axes. Each stem is provided on the end thereof exteriorly of the housing with a rigidly attached small gear which meshes with a large ring gear exteriorly of the housing. Actuator means are provided exteriorly of the housing to adjustably rotate the ring gear in opposite directions to effect simultaneous adjusting movement of the rear section of all stator blades. The actuator means comprise a manually operable power assisted actuator and a power assist assembly.