the only "proper" way to tell is to stick it on a 4wd rolling road and see what happens
the front will turn a lot slower than the rears

but you can always look for a muddly field and see if you get stuck or not

the official ford way to test it is to lift the front wheel with the other 3 on the deck and see how difficult it is to turn it
less than 70 or 90 nw on the torque wench means it's goosed, but remember to put the gearbox in nuetral