Deferred maintenance appears to have come home to roost.

I bought the megasuburban two years ago knowing it was a big old beast.  2004 quadrasteer with 200K on the transmission and chassis but 100K on the motor (6.0 and circa 2008).  It started leaking transfer case fluid but seemed to keep trundling along.  The other day I took it to a local (and trusted) independent mechanic for a work up. It needs:

1.  Transfer case has a hole in it. 

2.  All 4 front ball joints

3.  Both front wheel bearings

4.  Sending unit around fuel pump has rusted through (explains why it leaks fuel if filled over 7/8ths full)

5.  Power steering pump leaking at front

6.  AC was a bit down on freon

I gave him permission to go ahead and take care of the AC and the fuel tank.  I looked up the ball joints and wheel bearings and it looks like I can buy new parts online for $185 and tackle that work myself.  The PS pump will be ignored for the time being, the leak is really minor.  That leaves the transfer case.  I need to find one (selec trac 4 button) if anyone knows of a good source for a part.  I'll be tackling that work as well but it looks like the sort of thing I'm competent at.

How big is the hole?  If it's a crack/hole away from a dealing surface could you just clean it up and close it off with JB Weld Steel Stick?

This sounds like it describes the cause and a pretty efficient solution to the trans case problem 

https://www.midwesttrans.com/nv246.html 

Pump rub!

Ahhhh, the old hole in the transfer case. Happened on a co-worker's 2500HD. Kept trying to find used ones but they were non-existent because they either A) had already been grabbed up or B) had had the same thing happen to them.

Pump rub.

Dorman makes a new and improved housing for the transfer case.

$500 in parts plus an afternoon of your labour and it will be fine again. It sounds like a bigger job than it really is.

Used ones are non-existent because the labour to swap in a transfer case that already has the same problem vs actually fixing the problem are so close it doesn't matter.

The leak answers above are good advice.  The other solution for the T-case is to replace it with one that has a steel bar hanging through the floor to control it.  You know, one with gears and stuff instead of pumps and clutches to engage the 4wd.

So I have this.  Lots of GM codes that mean something to somebody.  How many of these codes are required if I find something out in FB/CL land?

would this work?

It says it’s out of a 2002 1/2 ton.  Low mileage though.