I recently purchased a 91 W150 5.2 auto with a 241D transfer case. I am trying to understand why the vehicle has to be in motion before the front drive shaft will engage. It has mile marker hubs, I am use to shifting to 4H and go. I got stuck a few weeks ago and the only way to get out was to jack the front end up in neutral and rotate the front axle by hand until I heard the transfer case engage the front drive shaft. As long as you are moving forward or reverse it will engage every time.