Abstract: A transmission for high-speed track-laying vehicles or vehicles with non-steerable wheels having an engine adapted to produce substantially constant power over a wide range of speeds comprises a gearbox and a hydrodynamic torque converter. The transmission further comprises reversing gearing and epicyclic output gears. A positive clutch couples the hydrodynamic torque converter to the gearbox output shaft. Two freewheel clutches are respectively driven by the vehicle engine and by the hydrodynamic torque converter. By this means the highest drive speed is selected at all times. The transmission further incorporates steering means adapted to procure continuous variation of the turning radius. The transmission is particularly suitable for tanks.