In a previous paper, a series of analytical formulas were presented enabling accurate predictions of churning losses for one gear which is typical of automotive transmission geometry. However, this formulation does not take into account the influence of flanges and deflectors. In order to extend the proposed methodology, a test rig has been set up in which several moveable walls can be inserted thus making it possible to modify the radial and axial clearances, i.e., the distances between the tested gear and the walls. Based on a qualitative evaluation of the various fluid flow regimes possible in gearboxes, the influence of the global volume of the oil sump on churning losses is analyzed. By considering a number of flange and deflector arrangements, the following conclusions are drawn: a) radial clearances have a weaker influence than axial clearances and, b) power losses can be minimized by properly chosen axial clearances.