Bearings are what allow the gears to rotate efficiently. They are generally created away from bronze or brass, they usually fit into races (or grooves) from the gearbox housing. That is why manufacturers arrived up with inside filters. These filters can be found on numerous modern-day automatic transmissions. Internal filters https://filtergearbox97429.blognody.com/35904778/the-fact-about-filter-gearbox-that-no-one-is-suggesting