Nowadays, the required standards of automotive manufacturing involves complex studies with purpose of the fuel and noise reduction produced by the autovehicles in functioning. Shape optimization of the car body involves lowering the aerodynamic force on the car; the airflow must be have a more laminar distribution. The aims of this study are to determine the airflow distribution in functioning of the truck with trailer and the method to decreasing the drag coefficient. In the first part of the paper are presented the studies and graphical methods used to determine the airflow simulation. Using the CAD design and the modeling techniques, the body shape of the truck with trailer is modeled in SolidWorks software. The geometry is inserted in a virtual wind tunnel created in the Flow Simulation module. The virtual environment created imitates the real working conditions. The aerodynamic model is tested on the 25 m/s velocity of the truck. After running the simulation, the obtained results are analyzed and the shape of the truck is improved with air deflectors in the space between the cabin and trailer. Rear side of the trailer is slanted to reduce the swirl flow and the vacuum volume. All obtained result are compared, establishing the optimal geometry of the bodywork. The end of this study presents the conclusions and the future research.