2008 Polaris ATV Sportsman 300 400 H.O. Service Manual, Page 143Get this manual
CVTTRANSMISSION 6Remove input shaft, counter shaft, and shift drum as an assembly11Inspect the shift drum tracks for wear or damageInspect shift fork for bending and the surface for wear, burning, or scoringInspect Shift Fork
Clean all partsRemove seals from gear case and install new using an appropriate size seal driverInspect all bearings, gear teeth, and splines for wear or damageInspect gear dogs carefully and replace if the edge of the dog is worn or rounded, chipped, or brokenInspect the reverse chain for damageBearings Reverse Chain Gear Teeth