My dodge 1500 Ram truck works in two wheel drive, but the four wheel drive doesn't work. How do I fix it?

Does it make a sound when you put it into 4 wd

Does it have a shifter to put it in 4x4 or a knob cause it's electric if it's electric make sure the motor on side of transfer case is working have someone get into the truck and turn the knob from 2 wheel drive to 4 wheel drive you should hear it shifting if not tap on the motor with a hammer see if it goes in if it does need to change the motor not to expensive should be right around $100.00