Load-independent power losses, namely windage power losses, are of big concern when the gearbox is loaded without oil lubrication. Air and/or oil mist are the fluid medium and should be studied before the addition of oil churning and squeezing losses. In this study, firstly, two dimensional computational fluid dynamics (CFD) approaches are followed to understand the behavior of the medium around the shrouded, rotating spur gear for the 40 teeth geometry of Seetharaman and Kahraman. For the sake of simplicity and fast convergence, periodic boundary conditions are employed with addition of carefully selected turbulence models in ANSYS Fluent 18.2. In the second part, same boundary conditions are applied to three dimensional study for the 23 teeth geometry of Seetharaman and Kahraman. Secondary flows and pressure contours are captured well. Windage power loss calculations are compared with the numerical study of Chaari et al. for different angular velocities for two-dimensions. As the result, qualitative behavior of windage power loss change vs. angular velocities matched well with the literature. Currently, three dimensional single spur gear and spur gear pairs are studied for the calculation of windage power losses. They will be compared with experimental data of Seetharaman and Kahraman.