Trucks (Lorries, pickups, etc.) from a long time ago are used to carry loads with different sizes and weights. Pickup has a big role in the traortation and distribution of goods and equipment in towns, so that the consumables distribution system of citizens largely depends on this type of vehicle. Appropriate size and portability of these vehicles has caused these vehicles be the best choice with acceptable time in busy urban areas. Various types of trucks are commercially available, but all of them have a fixed load floor that isn’t capable for vertical movement and so need to the specific equipment and techniques for loading and unloading. The use of this equipment increases the cost and reduce safety and occupy the load compartment. In a study conducted by Mokhtari et al. a mechanism designed for the rear pickup to help loading and unloading operations. Designed mechanism that is applicable on a front-wheel drive pickup, includes the capability to rear of vehicle that can be moved vertically. The aim of this study is to investigate the dynamic behavior of the vehicle. In this regard, the front chassis of selected pickup is modeled in Catia software and attached to the rear of the previous design and physical properties of the model is extracted. As well as complete vehicle model in order to achieve optimum stiffness coefficient and damping coefficient of dampers by multi-objective genetic algorithms in MATLAB software in order to reduce the acceleration and displacement of vehicle body is optimized. Front suspension of selected pickup is MacPherson-type that modeled in the Adams / Car software and after verification of compliance with the real model, the necessary analyzes to test the wheels parallel motion, reverse motion and static loading on the tires performed and the results were analyzed. Also, the steering system as geared-shoulder is modeled and analyzed. Following the initial suspension is modeled and analyzed. Finally, the original and the modified model of vehicle, is analyzed and compared. Keywords: pickup, vehicle dynamics, optimization, suspension, steering system, full model of vehicle
