I got my 89 F150 out in the snow awhile back and thought it was in 4 low and got stuck. Come to find out my ratio changed into low range but never locked the front tires. I was told the front drive shaft was turning does this narrow it down to the manual locking hubs?

 

It does sound like the hubs are not locking.
Can't help you with determining why, though someone else may be able to offer some suggestions.

Good luck.