Contaminants can enter your gearbox oil as a result of vents or even the fill tube in the course of examining/filling. Most of the time, on the other hand, contaminants are the result of normal use. The gearbox filter guards towards these contaminants which can help improve gearbox daily life. https://archerbrlym.therainblog.com/33001928/the-best-side-of-filter-gearbox