In this study, a nonlinear 3-D mathematical model for horizontal drum type washing machines is developed considering rotating unbalance type excitation. Nonlinear differential equations of motion are converted into a set of nonlinear algebraic by using Harmonic Balance Method (HBM). The resulting nonlinear algebraic equations are solved by using Newton’s method with arc-length continuation. Several case studies are performed in order to observe the effects of orientation angles of springs and dampers between drum and the cabinet. In order to reduce the steady state vibration amplitude of the drum, suitable orientation angles of the springs and dampers and their implementation locations are identified. Moreover, in order to further reduce the vibration amplitude of the drum at high frequencies, instead of viscous dampers, dry friction dampers are introduced to the system. Effect of orientation angles and parameters of the dry friction damper and springs on the force transmitted to the cabinet are studied.