94 Explorer 4x4 doesn't work

Hey everybody
The ol' Ford decided that in 12 inches of snow that the 4x4 won't work. When I press the button I hear the relay and then the light comes on. I can hear the shift motor engaging but the front wheels don't go into 4x4. I tapped the shift motor with a mallet to see if maybe it was gummed up but I would think that it is working because I can hear it when I press the button. Could it be the hubs are just shot? Is there something I am missing here? It makes you think the 4x4 is working but it isn't .
Thanks
Mike

I used to have a '91 and I sure wish I new about AF back then. Sounds like the same problem a lot of others and I have had. Check out this link.

http://www.automotiveforums.com/vbulletin/showthread.php?t=334898

I'm almost possitive this will help.