A device for selecting the ratio of the gearbox on a vehicle. The ratio is selected by electronic means which include a system for putting the engine speed under the control of the shaft speed, a system defining the ratios allowed, a system for introducing a parameter imposed by the driver, and a safety system with display and alarm means. Electronic memory devices permit taking into account the operating conditions of the engine. The device permits automatic or manual selection of a gearbox ratio corresponding to the greatest allowed ratio.
