A differential gear system employs stably-oriented orbiting gears to convey drive torque from a drive shaft differentially to a first wheel shaft and to a second wheel shaft. A portion of the drive torque is conveyed to the first wheel shaft, and the remainder of the drive torque is conveyed to the second wheel shaft. The differential gear system uses a first stably-oriented orbiting inner gear to convey torque to the first wheel shaft and a second stably-oriented orbiting inner gear to convey torque to a second wheel shaft. Dual-axis couplings allow the stably-oriented orbiting inner gears to move in a translational, orbital motion, but prevent the inner gears from rotating. Each of the stably-oriented orbiting inner gears has outer teeth, whose surfaces are substantially planar. The outer teeth of the stably-oriented orbiting inner gears mesh with flat-surfaced inner teeth of hollow gears.