Straight-tooth bevel gears are the simplest type of bevel gears that can be used for power transmission between intersecting shafts. They are commonly referred to as straight bevel gears, for brevity. Shafts for power transmission with straight bevel gears are usually mounted at a shaft angle of 90°, but straight bevel gears can be designed to work at a wide range of shaft angles. Straight bevel gears are widely applied in low-speed applications or static loading conditions where transmission errors and excited noise and vibration are not a concern. Therefore, a niche for their application has been found in differential drives, in which the speed is low and the load type is mainly static [5].