2009 Polaris Sportsman 850 XP EFI EPS Service Manual, Page 164Get this manual
TRANSMISSION Transmission Assembly
Thoroughly clean the transmission case halves and shaftsInspect all seals and O-rings for damageIf transmission was disassembled, seal and O-ring replacement is recommended (see exploded view above)If the cam shift shaft was disassembled, install the detent gear with the step facing the O-ringStep