Abstract: A device designed to actuate the positive clutches of gearbox sliding gears following synchronization of the respective pairs of gears. A cylinder mechanism is provided on each sliding plate of the gearbox, as well as solenoid valves which are controlled by an electronic calculator to select and actuate the cylinders. Each cylinder mechanism includes two oppositely acting pistons, each connected to the sliding plate, and each sliding in its own cylinder which also includes a return spring which operates against each piston and which practically eliminates the clearance above the piston as the piston is about to be actuated.