4X4 not engaging?

Hi
when you push the button two things happen.
The first is a elec motor on the side of the transfer case puts the transfer case in 4 wheel drive.

The second is locking the front axles so they spin the wheels this is also done with an elec motor. Or with auto locks depends which your truck has.

An easy way to tell jack the rear wheels up have someone look under the truck put in drive is the transfer case shaft turning while switch in 4x4 position. If yes prob in front axle.

If no prob is in transfer case actuator.

Either one of these motors can usually be disassembled and cleaned. This will normally repair the prob. If not they need to be replaced.

Hope this helps. Feel free to write back. Billymac