2005-2008 Honda ATV TRX500FA/FGA Fourtrax, Rubicon Factory Service Manual, Page 245Get this manual
SUB-TRANSMISSIONGEARSHIFT LINKAGE Install the countershaft assembly and reverse idle gear as setREVERSE IDLE GEAR
COUNTERSHAFT ASSEMBLY Install the mainshaft onto the automatic transmission unit and into the crankcaseInstall the washers onto the reverse idle gear shaft and countershaftInstall the shift forks and shaft (page 12-8)WASHERS