Abstract: To increase the top speed of a multi-speed range hydromechanical steering transmission for tracklaying vehicles, the displacements of the hydraulic motors in the two hydrostatic drive units are abruptly destroked from 100% displacement to 80% displacement at the moment the infinitely variable displacements of their respective hydraulic pumps achieve zero displacement during acceleration through the highest forward speed range of the transmission.

Abstract: The reversing mechanism (10, 200) for the motor drive comprises an electric motor (39) which drives a shaft (41) having mounted thereon a first gear (44) and a shifting mechanism in the form of a flywheel (100). The first gear (44) engages a second gear (37) which engages a third gear (38), the second (37) and third (38) gears being mounted upon a carrier mechanism (12) and each engageable with a driven gear (31). The carrier mechanism (12) is engaged by a cam mechanism (60). The shifting mechanism (100) engages an axial mechanism (70) which when displaced by the shifting mechanism (100) causes the cam mechanism (60) to rotate. Rotation of the cam mechanism (60) causes displacement of the carrier mechanism (12) so that one of said second (37) and third (38) gears disengages the driven gear (31) and the other of the second (37) and third (38) gears engages the driven gear (31) in order to effect a reverse direction of rotation of the driven gear (31) when the motor (39) recommences operation.