locking hubs?

[ONAGER]

i have a 2005 ford excursion, it has the 6.0, and is a 4x4

the truck has after market rims and center caps that cover the front hubs. the truck has the switch on the dash for 4x4.

My question is, the stock pics i have seen of the truck all the rims have the hubs exposed, so it looks like you can lock them...

if you have to lock the hubs, what is the point of having 4x4 on the fly shifting on the dash?

also, since the center caps cover my hubs, either they are locked or not, im gonna take the wheels off to see where it is at, but any problems either way?

[charlie101]

The shift on the fly 4x4 button uses vacuum pressure to lock the front hubs. If the vacuum isn't working you can manually lock the hubs from the axle. Don't lock the hubs unless you need to be in 4wd.