Originally Posted by lokitim59
If I check as you say & it still doesn't work, what could be wrong?
If the front axle disconnect is functioning properly, that would leave the transfer case.
Unless, (just thought of this) something is broken in the front differential. This could be checked by jacking both front wheels up & on stands, then turn front driveshaft by hand (transfer case in neutral) & see if one tire up front turns.
If it does, have someone hold that still while you turn the drive shaft again. If the other wheel turns. Then the diff is probably OK if you didn't hear any crunching sounds.
If the transfer case doesn't lock both drive shafts together, when in 4WD then it's something internal in the transfer case.
Your options then would be to take it down & either open it up to see if you can find something wrong, or replace it with a new (very expensive) or used/rebuilt unit.
If you look in there & find something broken, then you'll have to decide whether it's worth fixing.
Before you do anything, you should check that the posi-lok cable is actually engaging the collar in the axle.