This work presents the results and methodology of a dynamic durability analysis considering the interaction between crankcase and crankshaft. The approach is based on a robust mathematical model that couples the dynamic characteristics of the crankshaft and crankcase, representing the actual interaction between both components. Dynamic loadings generated by the crankshaft are transferred to the crankcase through flexible 3D hydrodynamic bearings. This methodology is referred to as hybrid simulation, which consists in the solution of the dynamics of an Elastic Multi-Body System (E-MBS) coupled with the Finite Element Methodology (FEM).For this study, it was considered an in-line 6-cylinder diesel engine used in off-road applications. The crankcase design must withstand higher loads due to new calibration targets stipulated for PROCONVE (MAR-I) emission regulations. The main objective for the block definition is to pursue design changes with minimal impact in current applications, utilization with high number of carry-over parts and cost savings.As results, the crankcase fatigue safety factors are presented showing the benefits of the adopted methodology, which enabled fulfilling the objectives of the project through small changes in the component. The crankshaft operational stresses and safety margins are also presented in this paper.