At the risk of irritating some others by resurrecting this old thread, there is a report on renovation of a Joule hub on "Hubstripping" here: https://hubstripping.wordpress.com/2...le-dynamo-hub/
This was a Joule I hub, and the process may not apply to Joule II hubs. Joule III hubs are made by Shutter Precision, and apparently can be overhauled by the factory. I haven't had the opportunity (read "need") to service my Joule III.
Note that all these hubs have a "notchy" feel to them when you spin the axle off the bike. This is from the strong attraction between the rotor (magnets with many "poles") and the stator (coils). Once the wheel is on the bike, it spins much more freely, though it spins down faster than a non-dyno hub. When you ride, you will not notice the resistance, even with the light on.
I recently found a SP hub on sale and picked it up for future building into a wheel for my road bike. This brand-new hub feels like a pepper mill when the axle is turned!
Steve