After unplugging the smaller 6-pin connector from the VTG control unit, I was abe to duplicate JP-X3's trick to unlock the transfer case clutch pack and transistion from 4WD to 2WD by applying battery positive +12V to the larger red wire. The larger brown wire already had ground, so my connecting that brown wire to battery negative was apparently redundant. It transitioned from 4wd to 2wd so quickly that I wasn't even sure it had done anything until I test drove to confirm success.
Just wondering: Could applying a negative voltage to the same red wire re-engage the clutch-pack to switch it back into 4wd?