No 4WD

So I guess recheck the limit switch voltages and see if something changed.

 

New limit switch voltages

 

Looks like the ADD is still having a problem, have you taken the cover off the ADD to make sure it's not all corroded inside?

 

So the add is new(I replaced it when I first had the 4x4 problem), but yesterday i took it off and took it completely apart and everything looked good inside. No corrosion and the soldering looked intact.

but in reference to what 20JAGCanada
said about the transfer case actuator… that was another part I threw at it in an attempt to get the 4x4 working… could it be that it was put in in the wrong “gear” when it was installed?

 

Well I mean according to the limit switch voltages the Transfer Case Actuator is shifting into 4wd but the ADD is not moving.
What's kind of odd is it worked when it was removed from the axle, are you sure you have it engaged properly in the sliding collar and the collar moves freely?

 

The collar was moving freely and the actuator (when removed from the front axle but still plugged in) moved into 4x4 when switched on, but didn’t move back to 2x4 when switched off.

 

that tells me most likely one of the front actuator limit switches is bad

 

I'd follow @Dm93 and @6 gearT444E suggestions first. I thought the table you posted was showing the resistance between the 6 points in the tcase actuator was off but I realize now you posted the limit switch voltages.

 

Ok, sorry if this is a stupid question, but does that mean I need a new front actuator or is a bad limit switch something I can fix?

 

I mean it looks like it didn't move at all, really need to backprobe Pin 1 (Red) and Pin 2 (Black/White) at the ADD Actuator, put a test light across them, have someone operate the 4wd switch while you watch the light, and see if it lights up.

You can also check connector EC1 (it's a short way from the ADD connector, just follow the harness back) for corrosion.

 

Ok so the test light came on when switched into H4 and L4 and was off in H2. I wouldn’t see any corrosion on EC1 but it was completely covered in grime.

 

Well if the test light lit when backprobed across pins 1 and 2 of the ADD Actuator and the actuator didn't do anything I would say you have a faulty actuator.