An analytic technology able to rapidly and accurately predict oil flows and churning torque in a transmission has been developed.The new method uses the finite difference method for analysis; with regard to wall boundaries it reproduces the shapes of physical objects by imparting boundary information to cells. This has made it a simple matter to treat the rotation and meshing of the gears, which form oil flows, and has also reduced the calculation cost. Tests of single-phase and multi-phase flows and churning torque were conducted in order to verify the accuracy of the new method. Calculation results for the flow velocity fields produced by rotating bodies, the trajectory of oil, and the behavior of the surface of the fluid displayed a good correlation with test results. Considering air entrainment in the oil, the ability of the method to reproduce these phenomena at high speeds of rotation was also increased. The method also displayed good reproduction of changes in churning torque produced by differences in the speed of rotation of the gears.The new technology was applied to a manual transmission, and CFD results for oil flow and churning torque displayed a good correlation with results from an actual transmission. In addition, the calculation time until the oil reached a quasi-steady state at 30 km/h was approximately 4.5 days.