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I was gifted a "normally open" vacuum switch after a discussion with a friend who has access to that kind of stuff. The vacuum switch is connected to an upfitter switch. When the upfitter switch is "on", it closes the normally open vacuum switch and it stops vacuum to the auto locking hubs. You can then switch to 4Lo. The transfer case shifts, but no vacuum flows the the hubs, so now you are in 2 Lo. The vacuum switch is not polarity sensitive - power to one of the parallel spades, ground the other.
The install was as easy as inserting the vacuum switch in line, after, the factory vacuum relay and the auto locking hub vent valve. I just zip tied the switch to the vent valve.
If you are already in 4Lo, then power the vacuum switch, vacuum to the auto locking hubs is stopped, and it takes about 30 seconds for the vaccum in the auto locking hubs to bleed off - then you will be in 2Lo. No wire splicing, no check lights, easily switched back to factrory vacuum system.
