Due to the possibility of producing shapes that met high standard characteristics and were unfeasible by traditional manufacturing techniques, additive manufacturing has quickly attracted the aviation industry interest. This led to the creation and redesign of a large number of components. The growth in computer softwares capabilities and computational power helped this process and provided new tools such as computer-aided structural optimization. This work aimed to adopt a free size optimization analysis for optimizing the shape of an aeronautical gearbox housing manufactured using additive technologies. A fundamental step has been implementing and validating the model into a new finite element software environment compared to the already developed counterpart.