Ford 4x4 problem

I am having a problem with my 2005 f-150 4x4. it has the triton 5.4l with a 3 speed auto with O/D. when I try to shift from 2H to 4H on the fly it will not engage and if the rear wheels spin on some ice, there is a small grinding noise from the front end, however, if I stop and try to shift into 4h it still will not, I must first stop fully, then put it in neutral, then shift to 4h, then 4l and when I hear the front hubs engage, I move about 50 feet forward then stop and put in in neutral again then into 4h and its engaged,if I slip into 2h it shifts but I have to go through the whole procedure again to go into 4h, its really frustrating while moose hunting in the Canadian north.