4x4 issues i don't understand

[feelingthis]

Thanks for even looking at this guys. I am a nOOb here, but I am pretty good at working on vehicles. I have a 2005 GMC sierra and can't get the stinkin 4x4 to work. It's electric everything, I've got the thing off the ground(four wheels in the air) a couple times. The motor on the transfer case works because the second I put it in four wheel, the front drive shaft starts spinning. I would assume that pretty much ensures that the push buttons on the dash are working. I've replaced the front actuator and even taken it out the actuator and pushed in the front diff thing manually. If I turn the front drivers side really slow, the other will spin the opposite direction, but spin it with a bit of speed and it will spin by itself while the other axle kinda just vibrates. I thought transfer case module or front diff actuator at first, but they both seem to be working. The front diff isn't making noise though. Could the front diff still be screwed with no noise?