Contaminants can enter your gearbox oil by vents or even the fill tube for the duration of examining/filling. Usually, having said that, contaminants are the results of normal don. The gearbox filter guards versus these contaminants which can help increase gearbox life. Old automatic transmissions normally have metal mesh filters. https://edgarhtbjp.loginblogin.com/41448518/the-smart-trick-of-filter-gearbox-that-no-one-is-discussing