2006 Honda TRX680 Rincon Factory Service Manual, Page 497Get this manual
REAR DRIVING MECHANISM Install the shim and bearing onto the pinion gearNOTE: When the gear set, ring gear bearing, andor gear case has been replaced, use 2.00 mm (0.79 in) thick shim for initial referenceSHIM
BEARING
PINION GEAR
Press the pinion gear in the bearing until it is seated by supporting the bearing with the special toolTOOL: Attachment 25 mm I.D07746-0030200