With the work medium of automatic transmission fluid (ATF), torque converter (TC) functions perfect performances such as smooth start, torque amplification, and the peak load restraint, and these properties makes the TC most suitable for off-road vehicles.An idea on the integration of TC and synchromesh gear box with their respective advantages is explored and introduced in this paper; here the system is named as Hydrodynamic Synchromesh Automated Transmission (HSAT). An automated control system makes the gear box as an automated manual transmission (AMT). HSAT takes TC as the starting device and accomplish shift process through AMT. The flow field optimized TC structure and the match calculation among the three parts of engine, TC and synchromesh gearbox; made this powertrain system has a good performance and the ability to reduce the fuel consumption.Another work presented in this work is to reduce the fuel consumption through the transferring of the working point, when the vehicle driving on different road conditions. That means the transmission shift algorithm, TC lock-up clutch control strategy is optimized, to make the engine work at the optimum area, and fuel consumption is reduced.