A seat height adjustment actuator, comprising: a brake drum fixable to a seat, the brake drum defining an output opening (300a, 300b) and an outer brake race around the output opening; a brake hub rotatable within the outer brake race, the brake hub including: (i) a floor surface having a shelf rising therefrom; and (ii) surrounding the floor surface and the shelf, a wall having a plurality of brake cam surfaces defining an inner brake race; a pinion fixed to the brake hub and extending through the output opening to engage a seat adjustment mechanism of the seat; between the inner and outer brake races, rolling brake elements configured to wedge between the outer brake race and respective brake cam surfaces to lock the brake hub relative to the brake drum in the absence of an actuator input; a clutch drum rotatably supported adjacent to the inner and outer brake races, the clutch drum defining an outer clutch race, and having: (i) clutch tabs extending between the inner and outer brake races to unlock the brake hub by displacing the rolling brake elements in response to the actuator input; and (ii) a projection extending toward the shelf of the brake hub; a centering bias element supported by the floor surface to simultaneously engage the shelf and the projection for centering the projection over the shelf in the absence of the actuator input; a driver cam, for receiving the actuator input, rotatable within the outer clutch race and defining an inner clutch race; between the inner and outer clutch races, rolling clutch elements for transmitting the actuator input to the clutch drum and for permitting rotation of the driver cam relative to the clutch drum in the absence of the actuator input; and an exterior cup fixed to the brake drum to enclose the brake hub, the rolling brake elements, the clutch drum, the driver cam and the rolling clutch elements; the exterior cup having an input opening therethrough. a brake drum fixable to a seat, the brake drum defining an output opening (300a, 300b) and an outer brake race around the output opening; a brake hub rotatable within the outer brake race, the brake hub including: (i) a floor surface having a shelf rising therefrom; and (ii) surrounding the floor surface and the shelf, a wall having a plurality of brake cam surfaces defining an inner brake race; (i) a floor surface having a shelf rising therefrom; and (ii) surrounding the floor surface and the shelf, a wall having a plurality of brake cam surfaces defining an inner brake race; a pinion fixed to the brake hub and extending through the output opening to engage a seat adjustment mechanism of the seat; between the inner and outer brake races, rolling brake elements configured to wedge between the outer brake race and respective brake cam surfaces to lock the brake hub relative to the brake drum in the absence of an actuator input; a clutch drum rotatably supported adjacent to the inner and outer brake races, the clutch drum defining an outer clutch race, and having: (i) clutch tabs extending between the inner and outer brake races to unlock the brake hub by displacing the rolling brake elements in response to the actuator input; and (ii) a projection extending toward the shelf of the brake hub; (i) clutch tabs extending between the inner and outer brake races to unlock the brake hub by displacing the rolling brake elements in response to the actuator input; and (ii) a projection extending toward the shelf of the brake hub; a centering bias element supported by the floor surface to simultaneously engage the shelf and the projection for centering the projection over the shelf in the absence of the actuator input; a driver cam, for receiving the actuator input, rotatable within the outer clutch race and defining an inner clutch race; between the inner and outer clutch races, rolling clutch elements for transmitting the actuator input to the clutch drum and for permitting rotation of the driver cam relative to the clutch drum in the absence of the actuator input; and an exterior cup fixed to the brake drum to enclose the brake hub, the rolling brake elements, the clutch drum, the driver cam and the rolling clutch elements; the exterior cup having an input opening therethrough.