Vehicle transmission with multiple torque convertors

A hydrodynamic torque converter transmission comprising at least two hydrodynamic torque converter units connected in parallel between a main input shaft and a main output shaft, each torque converter including an input drive means in the form of a rotating casing drivingly connected to said main input shaft and forming therein a working chamber having therein a pump part including at least one ring of pump blades and a turbine part including at least one ring of turbine blades, output drive means including an output drive shaft drivingly engaged with the said main output shaft, first connecting means for engaging the pump part with the said rotating casing for rotation therewith, second connecting means for connecting the turbine part with the output drive means for rotation therewith, wherein in at least one of said torque converters, one of said first and second connecting means is completely releasable so that the part engaged thereat including all blades of that part, upon being released, is completely released so as to be rotatable relative to its respective said drive means, one of said releasable part and its drive means being a movable member movable axially relative to the other between a first position at which the connecting means connects that part to its respective drive means and a second position at which the connecting means is released, servomotor means for moving the movable member between said first and second positions, the releasable part being the piston of said servomotor such that a fluid pressure differential on opposite sides of said releasable part effects movement of said movable member between said first and second positions.