The stability of wagons is an important issue in railway industry especially in heavy haul networks. The stability largely depends on a number of factors such as loading conditions and wind conditions aerodynamic forces caused by crosswind, centrifugal force, and dynamic forces due to track parameters and characteristics. The different methodologies for study of wagon dynamics under different wind conditions and load factors as well as their implementation,are part of rolling stock standards. However these methodologies do not completely cover all issues for this field of research. This study presents new results for overturning due to cross winds and takes into account important factors such as real lateral track defects and estimated lateral coupler forces obtained from longitudinal train dynamics simulation for worst case scenarios. For this study, a combination of two simulation packages, CRE-LTS and Gensys multibody software, has been used.The analysis method is to complete a longitudinal train simulation with lateral defects and different wind loading parameters to obtain lateral coupler force data required for further vehicle dynamic analysis. The lateral forces are applied to a full multibody model to study the resulting wheel unloading and lateral to vertical wheel force ratio in order to determine compliance withthese parameters based on the existing standards. Therefore, in this paper, dynamic wagon behaviours are studied with the combined effectsof wind, lateral coupler forces, curving and lateral defectson a multibody vehicle model using computer simulation. The assessment methods are based on the estimation of the vehicle wheel unloading. The dynamic behaviour study combining these four factors will create opportunity in the new area of research.