Transmission Selector Mechanism

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 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) moving a first selector formation (64,64b) which is engageable with a first coupling formation means (66) on a first cam (60) which moves one (7′,54) of the coupling members, 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) engaging both coupling formation means (66,65) for simultaneous movement of both couplers (6′,53:7′,54) when selecting certain direction/ratio changes so that by appropriate movement of the selector members (50,52) the coupling members (6′,53:7′,54) can be positioned in the four possible positions either on the same side or on opposite sides of their respective neutral positions.