Well I gave up and pulled the case out, kinda rough without a transmission jack, but no real issues pulling it. I split the case last night and found a broken range fork (as I suspected). Unfortunately the clutch coil housing was grenaded in the process (I am assuming the fork failed first). A quick inspection did not reveal any gear or other damage. I will disassemble the rest of the case and clean/inspect everything and get the parts ordered. At least I know pulling the case was not in vain. Fork broke right at a point that is a stress riser. Either the part was clearanced there for some reason (will look at that tonight) or it's a poor design. Fork is more or less die cast pot metal, not a real impressive piece. Really not sure what caused the issue. I could not find any remnants of any fork pads so I wonder it they were missing from new (??). Truck had 3 miles on it when we picked it up in '93 and only my dad, son, and daughter, and me have ever driven it. It has spent very little time in 4WD.
Will try and post up some pics later.

 

Whelp, the truck will likely be down for some time. The clutch coil housing seems to be a unicorn. I have tried several parts suppliers in the US with no luck. I have a supplier in Canada doing a search for me now. I don't want to have to buy a used case for one part but it may come to that.
Case is cleaned up and the parts that are available are on order. I need to replace a couple of marginal bearings but I should be able to find those local. I want US made bearings so I really want to see before I buy. I have had poor luck with Chinese bearings in tractors. I learned my lesson with those.

 

I have heard of these forks getting broken.
Did someone magilla-gorilla on it? Sounds like this truck has had a good life with original owner.
Lookin' forward to some pictures.

 

I have no idea why the fork let go. I dropped it into 4L to back a trailer up in a soft pasture. Just wanted a bit more control. After that I could never get it back out of 4L. In all the shrapnel I was never able to find the pads for the range fork so perhaps they were never installed from new??? I don't remember a time when it was forced into low range. It has always been a bit cranky to get into low and oftentimes took a bit of coaxing by switching from N back to D or R to get things lined up but I never had to hammer on it. Where the fork broke there was a bit of porosity in the casting so maybe that was cause. I likely will never know. Other than a water pump 15-20 years ago this is really the first real repair I have had to do on the truck in 27 years.

 

Ok, finally took the time to upload some images of the mechanical destruction. Below is the broken shift fork, grenaded clutch coil housing, and damaged oil pump bracket.

 

So I managed to break the two parts that are not longer available; the oil pump bracket and the clutch coil housing. Fortunately after some searching I managed to locate a used housing in Florida and the oil pump bracket in Calgary. I now have everything on order and am now just waiting for parts. The clutch coil housing should be here on Tuesday and I will take it into work and Magnaflux it just to make sure it does not have any cracks. I am also going the local bearing supply house and get the bearings I need. After tearing the case completely apart the best course is to just replace the bearings since I don't want to be in there again. In the meantime I blocked the sealing surfaces on the case with 400 wet/dry paper and used WD40 for grinding fluid. I also honed all the thrust washers, snap and lock rings on flat plate using the same method I used on the case.
Built a couple of tools for pressing the tone wheel on the mainshaft and for pressing in the seals.

 

This is one of the most interesting things I've read all day. Good work on grenading and good work on fixing. Keep on keeping on🤘🤘🤘

 

Clutch coil housing arrived so magnafluxed it and all is well. I got it from Cobra Transmission in Sebring FL. The guy I worked with was great. He tore down 3 t-cases in order to find the best one for me. The hardest part to find was the first one to arrive. I hope to see the balance of the parts by next week. I ordered Timken bearings from a local supply house and those are coming from TN sometime this week. I could have used something off the shelf but I really wanted Timken as I have always had good luck with their stuff. I will take a couple pics of the press tools I made for the reassembly and post them up. The tone wheel is pressed on the mainshaft and you need a tool that will fit over the splines and press on the wheel. The length of the shaft is about 7" so it is a long reach. Also one of the seals is a bit of reach into the housing so I made a tool that will make that easier to press in.
Couple more shots of the destruction. Fortunately the damage looks worse than it is. The truck was not driven far so the shrapnel did damage anything else.

 

Update: So everything is now here and I have started the re-assembly. Taking it slow and deliberate. Right now I have the new bearings installed and the planetary gearset in and the annulus gear back in as well. Next up is the oil pump. I need to borrow an inch-lb torque wrench from work for the pump housing fasteners. I should have the case back together by the end of the week. The seal in the back of the transmission started to leak so I am going to replace it as well. Looks very straightforward. Probably better it started to leak so I get it taken care of with the case out.

Couple of pics before I started and of the press tools I made for installing the seals (worked great) and the tone wheel (have not tried that yet). Painted them SB orange so they would be harder to lose in the shop.

 

Quick note: The new range fork is slightly different in geometry and seems to have eliminated the stress riser that was in the OEM one. Maybe I should have bought a selector fork as well...….

 

Well ran into yet another issue. The case in the truck is a BW4401 as mentioned above parts have been a struggle to find. So I ended up with a clutch coil housing from a BW1370. Everywhere I looked it indicated that the housing would interchange. I went to marry the case halves last night and found that the coil OD was oversized to the housing ID. Seems like the truck wants to live out it's days in the barn up on blocks. I ended up chucking up the housing in the old Clausing at work and taking 0.025" off the ID. Should be enough to let me assemble everything now as long as the tolerance stack of all the associated parts are not at the corner case (then I will have to take another ~0.010" off the ID. Had a bit of an interrupted cut at the start but I used a carbide insert and took 0.005" each pass.
This repair has fought me every step of the way.....

 

UPDATE: Well it is finally back together and all seems well. Took a lot longer than I ever thought it would and not sure I want to ever do it again but it back up and running in time to put it to work hauling. I actually bought a transmission jack to help with the re-installation but it still took both my son and I to get the transfer case hung back under the truck. Worst part was that we did it during the stretch of days when the heat index was over 100F. Figure I will run it for a couple hundred miles and then change the fluid out of it just to be safe.
There she is, back on the ground, washed up, and ready to work again.

 

Nice work.
You are Chevy Man Master Mechanic.