Basically, it is recommended that non-linear analysis shoud be used with consideration for friction and etc., when engineers calculate to design the trunnion suspension system for heavy duty trucks. But non-linear analysis was very difficult. so linear analysis per piece parts was conducted under assumed conditions. According to this method, it is difficult to obtain the calculated values matching with experimental values, thus “trial and error” must be repeated consuming much man hours.Recently, accuracy of non-linear analysis has been improved by the progress of the super computer in conjunction with the development of soft-wear such as pre-post or solver.Now, non-linear analysis of the total suspension system was conducted by taking contact and friction between each part into consideration. while at the same time divergence of the solution was prevented by optimum modeling. As a result, analysis values were well matched with experimental values successfully reducing weight and stress. This analysis method made it possible to reduce development man hours as much as 70% when compared with the conventional method.