Jack up one side, spin the wheel, listen for noise, if it spins the pinon, the axle is not a locked front axle, if not jack up both sides, spin the wheel, dead man the pinon, can you still spin the wheel. if the tires are scrubbed way down, I think you have a broke SPIDER GEAR,, or shaft, no matter what , you HAVE to PULL the 3rd member,
If it is a busted 3rd member, it will be hard to steer, because the inner wheel cant go slower and the outer wheel cant go faster, this is the hop and jump you feel, one of the tires slipping, and why the tires are BALD
I have seen this before, only in rears, broke spider gear locks the rear as though it is a welded, locked rear, the whole back end of the truck bounced every time it took a cornerr
Pull the drain plug, drain the oil though a white rag, like a dish towel, see what shows up, then stick a magnet in to see what you can find