Abstract: Constants for reconstructing by straight line approximations a plurality of characteristic shift curves each plotting limiting engine load vs. engine speed are stored in a main storage. A speed counter furnishes a binary speed number indicating present engine speed and a load counter furnishes a load number indicative of the actual position of the gas pedal. Output logic furnishes address control signals selecting the constants stored in the main storage for a particular characteristic curve in response to the load and speed numbers and a present gear signal. From these a limiting load number is computed. A comparator compares the present load number to the limiting load number and output logic furnishes a selected gear shift control signal if the comparator output is indicative of the correct relationship between the limiting and actual loads for the desired shift.