Hydraulic transmissions are widespread in engineering due to their advantages: easy start, flexibility, simplicity, damping vibrations. These drives can meet to the operating systems of drilling rigs and intervention when they are powered by diesel engines, but also to certain transmissions in the petrochemical industry. The article deals with the numerical simulation of a group of actuating (diesel engine ? torque converter), using the Simulink modeling opportunities. Virtual model of the transmission allows the study of the link with the actuated system, aiming the adaptation to the modifications of load and the changes of throttle.