Methode for controlling gear changing mode for automatic gearboxes

The system provides control of the gear change in an automatic gearbox (19) and, in automatic mode, includes an electronic supervision system to determine the transmission ratio using a rule based on the intermediate values. A further system detects and takes account of priorities established by driver intervention in applying manual control to the gearbox. When the selection made by the driver is incompatible with the automatically determined selection, the gear selection reverts to automatic mode, and this remains in force until conditions are such that the driver-selected gear is compatible with the detected conditions.