A transmission selector mechanism for controlling a vehicle gear box to simplify selection of gear box ratios.

Abstract

A transmission selector mechanism for controlling a gearbox which provides forward / reverse direction and high / low ratios using two coupling members (6', 53:7’, 54) each axially slideable in both directions either side of the a respective neutral position to couple a selected one of a pair of gears (10,12:11,13) to an associated shaft (4,5). The mechanism includes a driver operated forward / reverse selector member (50) and a driver operated high / low ratio selector member (52). The forward / reverse selector member (50) moves a first selector formation (64,64b) which is engageable with a first coupling formation means (66) on a first cam (61) which moves one of the coupling members (7',54). The high / low selector member (52) moving a second selector formation (63,63b,63c) which is engageable with a second coupling formation means (65) on a second cam (58) which moves the other coupling member (6',53). One of the selector formations (63,63b,63c) engages both coupling formation means (65,66) for simultaneous movement of both couplers (6',7') when selecting certain direction / ratio changes so that by appropriate movement of the selector members (50,52) the coupling members (6',7') can be positioned in the four possible positions either on the same side or on opposite sides of their respective neutral positions.