roller bearings free up parasitic horsepower loss created and consumed during normal internal component rotation as well as increase the thrusting surfaces of internal components reducig thrust load .we use roller bearings in most of our th400s and some are fully roller including the center support.the use of bearing allows the reduction of operating clearances between internal components making the transmission more durable wil less run up against parts during power application.as far as prices go all good 400 should come standard with extra bearings in strategic locations.read up on the 400 section of our site for further information.