Bearings are what allow the gears to rotate effortlessly. They are typically designed from bronze or brass, and so they fit into races (or grooves) while in the gearbox housing. Synchro rings have enamel on them that mesh Using the tooth to the gears, and so they even have friction https://filtergearbox86308.dailyhitblog.com/39513260/the-definitive-guide-to-filter-gearbox