In heavy truck driveline system, the components often include clutch, transmission, transfer case, drive shaft, etc. A fluid torque converter could be equipped in front of the transmission in order to improve the starting performance. Meanwhile, a hydraulic retarder could be introduced for auxiliary braking so as to adapt the truck to the brake on long downgrade in mountainous regions. Thus, the driveline heat load would have a notable increase. Both the fluid torque converter and the hydraulic retarder would produce a large quantity of heat, and a special cooling system is needed for adjusting the transmission fluid temperature with which the gains are potentially very large [1]. The heat load for driveline is often calculated based on empirical formula. For the heavy truck, however, if the heat value is underestimated, driveline components would suffer from overheated damage. On the other hand, if the heat value is overestimated, it will lead to the oversize radiator and affect the underhood arrangement.
In this paper, we focus in the heavy truck with the gross vehicle weight of 80,000 kg, which is equipped with the fluid torque converter and the hydraulic retarder. The driveline model is built based on 1D simulation tool. The heat load of each primary heating component is calculated referring to the existing driving cycle and combining with the actual driving condition of the truck. On these bases, the parameters and the layout of cooling devices (such as the oil cooler) could be set for the heavy truck working properly in different driving conditions.