Ford F-150 (2004-2008) :: 4wd Won't Working And Making Noise?

2004 F150 Super Crew Lariet 4x4 with limited slip. Center console with electonic switch 2wd/4hi/4lo on dash right of steering wheel. My 4 wheel drive does not work.

When the truck is in 2wd I have no issues, no sounds(I've heard anyway) or anything. The only questionable is when turning with wheel at full lock in either direction at low speed, my front wheels grab/lunge. Not sure if that is normal or not on these trucks.

When I put it in 4wd in the snow, it acts as though it wants to engage, but the second any power is applied to the wheels, the back wheels just spin and it makes a higher pitched grinding/chattering noise up front. It will also lightly clunk into 4wd with little power applied to the wheels, but once it has accelerating power applied the front diff "pops" and is clearly no longer engaged.

When in reverse in 4wd, it makes no noise, but still doesn't work.

Yesterday I had it in the shop for an oil change and to rotate my tires. While it was all off the ground I turned the ignition on and put it in 4wd. Both back wheels turned it the same direction(limited slip) as they should, and the front left wheel turned fully engaged with them. The front right wheel did nothing and turned freely on its own(assuming because front it open diff?). One oddity noted, when the back wheel were rotated one full revolution, the front rotated 2 full revolutions(also assuming this is because of the front diff being open and rear being locked?).

When I spun both front wheels by hand regardless of 4wd turned on or not, IIRC, they both made a clicking/ratcheting sound as the spun.

I left it in 4wd when I brought it back down on it's wheels and backed it out of the shop into the unplowed area of snow, I lunged the throttle a touch and the front end dropped as the front wheels gripped and slightly broke loose in the sticky snow. It was fully engaged and working properly for a second. I then put it in drive and tried to move forward, soon as any power was applied it "popped" out of engagement in the from diff and was back to 2wd and light grinding noise.

Another note, our first big snow fall a few days back is when I first had a real issue with the 4wd not working at all. It had snowed pretty well and I didn't feel like shoveling the driveway because I was running short on time to make it to work and my wife had the day off work and didn't need to go anywhere. I started it, put it in 4wd, let it warm up a bit, proceeded with trying to leave. This is when it all began with the 4wd not working at all and grinding. As it made that noise, it sounded pretty light to me in the cab even with the window down. But, as my wife noticed me stuck in the driveway she stood in the front door watching with the glass storm door still closed. She said she thought that "light" grinding noise I heard, was actually quite loud from where she was standing, 60+ ft away.

Previous issues I've noticed with my 4wd that may diagnose my exact issue, it has had a frequent issue the past year or so with, when engaaged, if I applied too much acceleration, from a stop or not, it would suddenly "pop" out of engagement as I've previously noted on, but I would immediately let off the throttle and it would reengage right away.

On two other occasions, it has refused to engage into 4wd no matter what. I simply contributed it to the extremely cold weather during the occurrence, as it worked just fine the next day and/or the next time I placed it in 4wd.

4hi/4lo light always lights up in the gauges as they should and as if everything is working normal.

So, IWE's? Actuators? Vacuum?