This master thesis has the goal to test a new structural optimization method, to redesign an aeronautical Gearbox, in order to make it suitable for Additive Manufacturing production. In particular way we will focus on the TGB (Transfer Gearbox) which is the part that transfer mechanical motion from compressor shaft to the auxiliary gearbox where are placed the alternators to transform mechanical energy into electrical one. During the optimization process we will try however to reduce the component weight, taking into account all the constraints. The Optimization method chosen for this work is made available by Altair Hyperworks and it is the Free Size Optimization.