It sounds like you have a wheel bearing hub going out which allows the ABS wheel speed sensor to be off a little which makes the car think it is skidding and engages the 4 wheel drive to regain control. Do you hear any noises that are unusual in the front? We should run the codes as well. here is a video to show you how for the ABS system:
Here is how you replace the front bearing hubs in the diagrams below. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
Images (Click to enlarge)
Thursday, January 16th, 2020 AT 12:37 PM