<p>Rotorcraft gearboxes are quite unique in the industry as they generally deal with high power, high overall gear ratio, low available space and a strong push towards weight reduction. The first reduction stage typically deals with very high input speeds. The main functional components (gears and bearings) typically require pressurized lubrication; when for any reason oil is not effectively drained away it can lead to overheating, especially on high-speed gears. Even if literature provides many examples both in academic and industrial environments, the specificity of each case makes it impossible to draw general conclusion. For the same reason, the current work is based on experimental testing on two cases shown here to exemplify the issue and its solution. The first example represents a Main Gearbox (MGB) where one of the Input Modules (first reduction stage) had a mild overheating issue. Upon investigation it was found that it got entirely flooded with oil; then, after further investigation, the issue was understood and easily solved. The second example shows a Nose Gearbox where an unexpected windage phenomenon prevented oil drainage to the scavenge pump, thus leading to extreme and almost instantaneous overheating of the module. The key result is that identifying the causes of the issues allowed to provide a quick and easy solution.</p>