This study develops a one-dimensional (1D) model to enhance transmission efficiency by evaluating power losses within a transmission system. The model simulates power flow and identifies losses at various stages such as gear mesh, bearing, churning, and windage losses. Using ISO/TR 14179, which provides a method for calculating the thermal transmittable power of gear drives with an analytical heat balance model, the 1D model ensures accurate thermal capacity evaluation under standard conditions. A key advantage of this 1D model is its efficiency in saving time compared to more complex 3D modelling, making it particularly useful during the conceptual stage of transmission system development. This allows engineers to quickly assess and optimize transmission efficiency before committing to more detailed and time-consuming 3D simulations. To validate the model, experimental tests were conducted at various motor speeds (RPM) and torque values, using high-precision sensors and dynamometers to measure input and output power. The data obtained from experiments aligned well with the outcomes predicted by the model, showing average relative deviations of 2.63% for efficiency. This methodology offers critical insights for improving design and performance of transmission systems in automotive applications. The validated 1D model serves as a reliable tool for optimizing transmission efficiency, this contributes to the advancement of more efficient and environmentally sustainable vehicles. Recent research, including the 2023 U.S. Electric Vehicle Consideration (EVC) Study by J.D. Power, supports this trend, highlight the growing consumer interest in electric vehicles and the importance of addressing transmission efficiency to meet market demands. Additionally, the development of new transmission systems for hybrid vehicles emphasizes the need for innovative solutions to enhance system efficiency and performance.