A power transmission device, in particular for a Diesel motor car is disclosed which comprises a hydraulic transmission and a mechanical transmission connected in series, the latter having low- and high-speed clutches, where in place of a direct drive clutch comprising a mechanical clutch that has hitherto been provided at the input side of the hydraulic transmission low- and high-speed clutches each comprising a mechanical clutch are provided in the mechanical transmission so as to serve as a direct drive clutch, remarkably shortening the time necessary for engaging the low- and high-speed clutch e.g. when the car is coasting with the low- and high-speed clutches disengaged.
