A single-stage gear reduction output mechanism for an automotive seat assembly includes a gear housing bracket, gear housing, axle shaft, eccentric, and first and second gears. The axle shaft extends through the eccentric with a slip fit, the first gear rotates with the axle shaft, and the second gear is carried on a first bearing surface of the eccentric and meshingly engages the first gear in a planetary arrangement. The second gear includes an external flange with at least two guide holes. First and second support pins that are rigidly fixed in place relative to the axle shaft extend through the two guide holes in the external flange of the second gear. Forces acting at the interfaces between the first and second support pins and the two guide holes and between the eccentric and the second gear prevent the first gear from back-driving rotation of the second gear.