We isolated the problem to the axle vacuum shift motor (page 3-33 if you’re using the full shop manual) and have decided to replace it in lieu of a pro-lock cable system. We may try that approach in the future. For now, isolating the problem to the Center Axle Disconnect (CAD) and the vacuum was best done while running the motor and having my assistant (wife) cycle the 4×4 selector with the right front wheel lifted.
Post time: Jun-21-2017