Abstract: This invention relates to hydrodynamic torque converters and in particular to improvements therein relating to the blade system and to the shape of the toroidal working chamber. For situations wherein a more or less distinct top speed is required, even when direct drive is not used, and where it is important to avoid the simultaneous existence of high torque absorption and low efficiency at high speed ratios, the blade system according to the present invention is advantageous, said system being characterized by a range of ratios for the radii of the outlet and inlet edges of the pump, turbine and guide blades as well as a range of angles .alpha., .beta., .gamma. and .delta. as herein defined.