Abstract: A motor vehicle four-wheel-drive transmission employs an interwheel differential gear in a first axle, and solely viscous fluid coupling device in a second axle for differential transmission of drive to the road wheels of the second axle only when a speed-difference is established between the first and second road wheels, the two axles being mutually in direct driving connection through respective propeller shafts commonly driven by a change-speed box. In one arrangement of axle with a viscous fluid coupling device, a crown wheel is mounted co-axially on a housing of such coupling device from which nearside and offside half-shafts extend driven by separate sets of "inner" annular plates interleaved with those of an "outer" set of annular plates driven by the housing. In another similar arrangement, two separate viscous fluid couplings are used, the housings thereof being driven by a common crown wheel.