This thesis explores the design and performance of hydromechanical transmissions, focusing on both input-coupled (IC) and output-coupled (OC) configurations. The study begins with an overview of hydromechanical transmission components, including hydrostatic systems and planetary gear trains, and examines how these elements interact in the different transmission configurations. Using Simcenter Amesim, simulations were performed to analyze the system’s behavior under various operating conditions, starting with a constant load scenario. For both IC and OC configurations, results highlighted unique power and torque distribution patterns between hydrostatic and mechanical paths, reflecting each configuration’s approach to handling power demands. Further simulations incorporated vehicle dynamics, evaluating speed response, output torque, and power ratios in both configurations.