Abstract: A system for determining the instantaneous torque produced by an engine or motor that drives on automotive vehicle powertrain through a hydrodynamic torque converter. A digital circuit operates to generate a binary number, which is the count of high frequency pulses that are a multiple of the frequency of the engine crankshaft occurring between the pulses that are proportional to the speed of the driveshaft. The speed ratio control elements of the transmission are controlled by the state of pressure solenoids that actuate hydraulic valves. The state of the pressure solenoids is used to determine the speed ratio of the transmission; changes in state indicate the onset of a period of instability during which the transmission components are undergoing transition to a new speed ratio. This transition is sensed by the circuit and a signal indicative of the transiency or constancy of the pressure solenoids is transmitted to the computer.