Ok....here are the simple observations from the test of the NV124 case on my workbench.
- Spinning input shaft by hand.....both output shafts rotate
- Spinning input shaft by hand and holding rear output shaft stationary.....front output shaft rotates.
- Spinning input shaft by hand and holding front output shaft stationary.....rear output shaft rotates.
Caveat....these tests were done with spinning by hand, which does not simulate rear world forces transmitted into the driveline.
Thus, my conclusion, you can NEVER make an XI into a rear wheel drive by simply disconnecting front driveshaft. It will just send all the power to the front output shaft and spin endlessly without putting power to the rear.