When the 4WD unit is not locked does this mean that the pinnon can not drive either the right or left axle? It looks like to me that it only separates the right axle and the left axle is still connected. This would make it easier to turn but front drive shaft still spins due to the left wheel not being disengaged. Correct?

Does the 4WD unit lock both sides together?

The reason I am asking is because I am looking into the 4L80E conversion. I dont have one of the trick input shafts so instead of that I was looking at converting to a HD 4WD TC since I already have one sitting around. Would I need to swap to a 4WD axle, though?

 

It's an open diff carrier. The driveshaft and carrier can in theory remain stationary because as the left axle continues to spin forward the right axle can turn backwards as it is disconnected from the right tire. All 4wd does in the front is connect the 2 piece right hand shaft.