remove electronic 4WD control andlock TC into 4WHI

[PapaSteve]

I have a 2000 1500 yard truck that is only used to plow snow.  When the front diff stopped 4WD I removed the actuator and replaced it with a welded 'plug' that held the diff engaged 24/7.  It ran for 4 or 5 years that way with no troubles.  Then the 4WD switches began not working right.  I had to push the buttons repeatedly until I could hear it go in.  Then it only had 4WD in 4auto a few storms before that quit, leaving the truck functional in 2WD only.  I took it to a repair shop, my guy said the transfer case was bad.  So I had him put in a used one.  I told him to remove the shift acutuator from the TC and lock it into 4HI manually.  That done, still no 4HI.  The front drive shaft makes a clunk inside the TC when wiggled like it is engaged.  What am I missing?