The crank-train is the main source for power development and is the bone structure, which needs to be robust against durability along with fulfilling the functional requirement. With the high specific power requirement and very high In-cylinder pressure, the light-weight crank-train development becomes a challenge. Various simulation tools are now available in the market, which predict the vibration and durability aspects of the crank-train in the very initial stage of development. However, in order to use these tools effectively and with high confidence level, the simulation model first needs to be established with the existing engines through correlation with other FE-solver and various validation processes. The more is the correlation and validation available, the faster and more accurate becomes the future engine development process. This further gives high confidence level to deal with complex systems, when engine vibration and durability aspects are considered.Similar approach has been used to first establish the analysis process with existing IL6 engine with test-validation that too, first with analytical approach through multi-body dynamics based 1-D simulation tool and then extended to 3-D detailed analysis. The well established process was then extended to develop IL6 diesel engine coming from same parent IL4 engine. The complete design-analysis process for IL4 crank-train is described in detail and within the scope of this paper. The 3-D detailed analysis is not being described in current paper in order to avoid any complexity and to keep the contents simple and easy to understand. However a very brief of 3-D modeling and related precautions are mentioned for IL6 engine, along with keeping the report more result-oriented for IL6 crank-train.