Hi all and thanks for having me; I'm trying to help out a friend who has a 2001 F250. My knowledge and experience with these trucks is zero but I was in the motor trade many years ago so I seem to be the one to get asked for help any time a mate has some kind of mechanical issue
He hasn't had the truck very long and has done zero off-roading with it so far, but a while ago he was at my place and trying to drive up a grassy hill where he needed 4x4. He could not get the front drive to engage, and there was a loud grinding / clunking noise coming from the transfer case when he tried to take off with 4x4 selected- kinda like a metal rod being run across a metal washboard, if that makes any sense. The front propshaft wasn't turning.
A while later he called me saying that he was under the truck and there was a massive amount of freeplay in the front output shaft. Like about 3/4 of a turn. Without knowing anything much about these transfer cases except that they're chain drive, we surmised that the chain was massively stretched and that the grinding / clunking noise we'd heard was the chain jumping teeth on the sprockets.
I suggested we drop the transfer case out and bring it to my place to strip it down and see what it looks like inside. He looked into just buying a reconditioned TC and decided that he would go that way. He was off work with a broken leg so needed to wait a couple of months before he could pick up some extra shifts to pay for the reco box.
The other day I helped him drop the TC out of the truck and with it on the bench, it's obvious that the chain is not stretched and that is not where the problem lies. We took the shift motor assembly off the side of the box and shifted it through H2-H4-L4 with a wrench on the shaft. It is VERY stiff to rotate the selector shaft. At one point, rotating the input shaft while moving the selector, the box produced the exact same noise described above (not as loud obviously), seems it was the front output teeth / splines trying to mesh but not engaging, grinding against each other.

With that longwinded preamble, here's some questions:
Is it normal for the selector shaft to be very stiff to rotate through the 3 positions?
He tells me he was rotating the TC selector switch with the truck stationary- should the truck be moving when you rotate the dial, to allow the teeth to line up? (might that be the whole problem right there??)
We put a battery across the contacts of the shift motor and it works fine both directions; how can we test the switch to see if it's giving the correct feedback? (the switch on the TC shift motor assembly, not the one on the dash)
I'm thinking perhaps the 4wd ring and collar might be damaged so they won't engage easily?
The TC is now at my place and the next step will be to open it up and have a look at these parts, but I'm wondering if the whole problem might be just in the shift motor or switch?