Originally Posted by
dave35
Rebuilding freewheels is such arcane deep magic that even Sheldon Brown says not to. It might be worth doing so if you have a really high quality close ratio freewheel (like a 13-18/19) and are willing to replace an unreasonable number of bearings individually in a procedure which sounds more like open heart surgery than bicycle maintenance. Instructions are on the same page where Sheldon says to never, ever resort to this.
It's really not that bad, as long as you're able to get them apart. There are several different lockrings and assembly designs available.
I see it more as a question of investment vs payoff. Apart from the balls, I've never seen any separate parts available. If disassembly reveals something else than gunk, you're left with replacing the unit anyhow.