Transmission shift pattern data representing different engine braking characteristics are stored in a memory [111]. The data is read out of the memory as a function of engine and vehicle operating conditions into a conversion circuit [113] where the data are converted into actuating signals supplied to one or more solenoids [2a to 2d]. Shift valves of a hydraulic actuating unit are controlled by the solenoids to shift the transmission pattern to a speed change mode which provides engine braking of an appropriate characteristic for varying engine and vehicle operating conditions.
