Abstract: Method for automatic gear selection in a vehicle power transmission, said selection being catered for by a control system including an electronic unit (1) which, in response to signals representing vehicle speed and engine load, coacts with a programmable read-only memory PROM (28), in which there are stored, for each gear position, alternative speed limits for changing gear to neighboring gears and also limiting values relating to speed change and engine load for selection between said alternative speed limits. To eliminate the risk of unsuitable gear selection for heavy vehicles, e.g.

Abstract: The invention relates to a method for preventing at a vehicle gearbox selection of an operationally erroneous gear in the absence of a gear change regulating speed signal. The absence of the gear change regulating signal is detected by a fault detection circuit or by a fault detection routine, which thereby sends an output signal to an operative circuit or the like. The operative circuit ensures that erroneous gear selection is prevented and/or triggers a fault indication.With the intention of ensuring that a fault already existing when the vehicle starts can be detected, the invention is essentially distinguished in that during the fault detection routine it is determined whether the engine is running, whether a forward gear is engaged, the clutch is engaged, and whether and with these conditions extant whether the speed has attained a given minimum speed within a predetermined time.