Bearings are what enable the gears to rotate effortlessly. They are usually manufactured outside of bronze or brass, and so they in good shape into races (or grooves) from the gearbox housing. Tough shifting, diminished gas efficiency, and burning smells are just some of the signs of a foul transmission https://filter-gearbox65296.ampedpages.com/everything-about-filter-gearbox-61046198