If your hubs don't have a grease fitting then you pry off the cap, take the cotter pin out, unscrew the bolt and remove the hub. Pull the seals and bearings, repack the bearings replace them and the seals and put the hub back together...I cheat, I put bearing buddy's on so I can keep them greased and I don't replace or repack the bearings unless there's an issue. Haven't had a bearing go bad on the snowmobile trailer yet. Frequent lubrication is key to happiness grasshopper.