The V6 transmissions are smaller outside and inside, all are a little weaker than the mid sized AOD's and 4R70W's, behind V8's. The V8 trans is capable of most needs, even plowing etc.
The real AWD in the few Fords that had it in mid 90's to about 2010 were made to try hold the same speed front to rear, not locking but resisting speed differentials. On slick ice usually one tire spins on front, and rear, unless the differentials have some kind of locking device. The OEM traction lock is fairly weak, when new or rebuilt they can resist up to about 75lbft of torque before they allow slipping of the low traction tire. The fronts were all open, so it is rare to ever hear of one with a locking front.
I got up and down a fairly steep hill covered in snow about 15 years ago in my Mountaineer. I had real snow tires and it did spin one front tire up near the top where it was the most steep. I have a Torsen in the rear of that one, it's a very good street diff. The tires did the most work, coming down was possible only from the tire traction(Blizzak 245/70/16's).