Access the freehub body
Take the wheel off the bike.
Dismantle The Left Side
Hold the cone on the left side still with a cone-spanner and loosen the lock-nut. Unscrew and take off the lock-nut, washer and cone. Catch the balls if they fall out. Count them.
Clean all the loose parts and the cups inside the hub. The cup on the drive side is part of the freehub body but you can treat it like the cup in a hub shell
Inspect The Bearing Surfaces
Check the surfaces – on the cones and inside the freehub body shell – where the balls run, for roughness or uneven wear. Worn cones can be replaced but if a hub is worn it may need to be scrapped.
If you need to replace the cones on the freehub body, measure the position of the one still on the axle, and make sure they go back in the same place so the axle is centred in the hub. The drive side may have more spacers between the lock-nut and cone. If you’re replacing the cones you may need different sized spacers if the new cones are shorter or longer than the old ones. It may be easier to replace the whole axle if you can’t find cones that match the thread on the old axle.
Repack With New Balls
Pack the races in the hub with new grease and press the same number of new balls – of exactly the same size – into the grease. Changing the balls prolongs the life of the other parts of the freehub body. If you’re not sure how many balls came out, or if you suspect that the hub was packed with the wrong number of balls, fill a race with balls and then take one out. The balls need room to roll around.
Assemble the other side and adjust the hub.
Remount the wheel in the bike.