Black'd F150

I see a lot of threads that talk about IWE and solenoid issues. Well I've torn the whole front end apart and replaced ball joints, hubs & IWE's. I didn't really see much on half shaft operation so I figured id ask. Once I replaced everything, I didn't install the brakes or rotors incase I still had issues. Started the truck up with the rear wheels off the ground as well on jack stands. Put it in drive, rear tires turn. Push brake in, click into 4 wheel drive hi in and only the passenger side spins freely. Take it out of 4 wheel and the passenger side doesn't spin. So that side seems to be working properly. The driver side was my problem side from the start. Now when its in 4x4 it acts like it wants to spin and if you spin the hubs by hand, it slowly barely spins but wont on its own. I've got vacuum when I should and when I shouldn't. I checked for sure by pulling the hose off which in turn, should engage the half shaft but nothing happens. The transfer case shaft to the differential spins nice and free along with the pass half shaft. So I guess would that mean theres something wrong with the differential of maybe the half shaft is toast? Or does it need to have a tire and pressure on it to engage? I figured it should spin like the passenger side does when theres no resistance. Any help would be awesome. Didn't want to tear it apart again if i'm missing something lol