these silly littel " rough terrane lawnmowers " have exactly what the op is on about. chain drive upto a shaft from both back wheels with a cabel operated clutch in the middel. the system actualy works. however the way its inplemented on said mowers is somewhat lacking mixed with the horrific hubs they use to widen the track and chocolate transmissions makes them a pos. but the way the difflock is done dose actualy work it chould be better enginnered tho