A system for adjusting a transmission ratio for a transmission built into a motor vehicle. Selection devices actuable by the driver of the vehicle are provided. With these selection devices, the driver can pregive pulses to change the transmission ratio. In a first component object, the pulse processing, pulses are detected whereupon in a second component object, the counter, count values are determined and stored in dependence upon valid pulses. In a third component object, the switch request, shift requests are determined in dependence upon count values and while considering pregivable peripheral conditions. The transmission ratio is adjusted in dependence upon the shift requests. With the defined interfaces of the objects, the exchangeability thereof is made possible whereby especially a reuse of the software is facilitated.