Introduced In this work is an innovative drive for wheeled mobile robots, that is based on two identical, coaxial wheels, independently driven by two identical motors. The common axis is capable of rotating about a vertical axis. The drive, termed dual-wheel transmission (DWT), is composed of two identical epicyclic gear trains, lying at two different levels and coupled by a common planet carrier. The latter can turn freely with respect to the robot platform carrying the motors, the transmission having as a stand-alone unit, three degrees of freedom and only two motors, which makes it underactuated. Upon coupling this drive with two other wheel units, which is the minimum required for static support, a robot with mobility of three is produced with the underactuation thereby disappearing. Finally, the dimensioning of the DWT is reported for robustness against manufacturing, actuation, and sensing errors.