2000 F350 V10 Gas dually not going into 4WD
 

Was stuck in the mud the other day with a boat behind me. 4x4 light comes on and it appears to engage when running but not from a stop. Hub appear to engage but front wheels aren't engaging. Any ideas?

Do you have a copy of the owner's manual, it should explain that when the hubs are in auto position, the vehicle has to be moving over 5 mph.
If the vehicle can't get any traction to go 5mph you may need to lock the hubs manually.

you could also have cracked vacuum lines that run to the hubs...