Truck acts like it is stuck in 4x4 ?

The #1 reason the truck gets stuck in four-wheel drive is the transfer case actuator motor goes bad, but you should check the fuses as well, here is the wiring diagrams for the system so you can see how it works, and which fuses to test for power this guide will help:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

If the fuses are good and you have already replaced the actuator motor assembly, I have seen the GEM go out in these trucks, you may want to do a CAN scan to see if any codes are stored.

You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Here is the location of the transfer case actuator motor so you can check it out. Check out the images (below). Please let us know what happens.