Abstract: An IC engine is connected via a clutch with a change-speed transmission. A sensor responding to a gear selection informs the electronic control circuitry in which gear the vehicle is traveling. The rotary part of a tachometer is provided at the output of the transmission and is in cooperation with the sensor part of the tachometer, which feeds a signal to the electronic control circuitry. A universal joint shaft runs from the output of the transmission to the axle transmission, which is connected via the axles to the drive wheels. The rotary tachometer elements, connected with the drive wheels, are in cooperation with the tachometer sensors, whose output signals are supplied to the electronic control circuitry and compared therein with a calibration value. Such comparison determines the optimum clutch engagement time for the respective travel and loading condition of the vehicle.