I have a 2000 dodge ram 1500 5.9 and I run it in 4wd all the time. When turning you can hear one of the front tires skirting like the diff is locked but when gunning it on ice one wheel spins.

 

First thing is jack the truck up and run it checking that the 4wheel is operating normally without being on the ground or turning.

There could be an issue in the CAD. Or it's merely a vacuum problem.

 

4x4 is really only 2 wheels turning (1 in front & 1 in the rear) unless you have posis (track lock as Chrysler calls them). Now if you are using 4wd on dry pavement where the tire can't slip you will get the tire chirp. Now when on ice only one front will spin, until it gets traction. Once it gets traction the other front wheel will engage.