Also, changing them for LEDs will of course involve a series current limiting resistor, probably around 800 to 600 ohms.
I'm interested in this centre differntial of yours though. Can I ask, what vehicle has this feature fitted? There are many four-wheel-drive vehicles that feature locking Centre Differentials (mine does infact), but I've never seen one where you vary the amount of lock. On mine you either lock the centre diff or you don't, and I can't immediately see any advantage to being able to vary the amount of lock?
Brian