Front wheel drive issues

Ive recently had the Kingpin bearings done becuase of play on the front wheels(66k miles so this work is nothign out of the ordinary) And when i had it lifted i have renewed all the vaccum sytems with nylon because of corrosion.
But now i cannot seem to get any power into the front wheels.

I can hear the vac hubs locking in on both sides,
and the front shaft is locking in with the transfer case
I have had each side lifted and in 4wd and low range the front wheel s can spin freely when lifted off the ground.
so i belive the problem is in the front diff no passing power from the shaft to wheels.
But im still new to 4x4s and would like some advice or ideas as to what the problem may be.

start it uo put it in 4x4 H or L range then jack one side at a time like you have and spint the wheel and see if the front prop spins with the turn of the wheel

You may have crossed the vacuum pipes over when you renewed them, and the hubs work backwards.

Engine running, select 2wd.
Crawl underneath, try and rotate front propshaft by hand. It should rotate freely. If it doesn't, likely the hubs are locked, because the pipes are crossed.

Engine running, select 4wd.

You won't rotate the front prop by hand now as the transfer box has locked it to the rear one, so jack up one front wheel.
Try and turn this wheel by hand, it should turn just a little, to take up play, then stop if the hubs are locked.

If it turns round and round, either the hubs are not locked, or the diff is broken.

To eliminate the hubs: Engine off. Undo the 6 bolts around the black hub and remove.
Stick a finger inside the splined part, wiggle and pull, and the splined centre will fly outwards and lock to the outer hub. Carefully replace and it will stay locked.

Do this both sides and carefully slide back on so they stay locked.

Engine still off, select 4wd, jack up one front wheel, and try to turn. If it turns, the diff is bust. If it doesn't it is ok, and the problem is with the hubs and vacuum system.

Also might be worth double checking you can hear both hubs engaging. If only 1 is engaging then you will be able to spin the wheels in 4WD.
Quite easy to block up the vac lines with grease by accident....

goatboy wrote: Quite easy to block up the vac lines with grease by accident....

Virtually certain if you have changed the wheel bearing.

Remove the black hub, and make sure you can blow through both spigot tubes on the hub casting. (you will not blow through them with the hub on)

Check that the hub seal is intact and running on the nice shiny lip on the hub nut.

Or take off both the vacuum hubs place in 4wd engine off and jack up one rear wheel hand brake off and turn wheel then see if the front half shafts turn then you no if your tbox and diff is ok