GM truck rear end help...

[Highway Star]

I need opinions and experience with full size GM truck/suv rears. Brace yourself, this is going to take a minute. I'm posting this in a few places because I need to get it straight, and quick, because I need to buy a truck yesterday. I have no wheels right now, except the Chevelle.

I'm looking for a used vehicle, got about $4000 to spend. My wife and I decided we need a full size truck/suv because we're likely buying a camper trailer of some sort soon, and will need something to drag it around with.

Anyways, the market here is such that for the $ I have to spend, I'm looking at mostly 150,000 mile+ extended cab trucks, tahoes, yukons, burbans, etc.

This is all being brought about by the POS hunk of wasted energy 2002 F$%^ exploder parked dead in my driveway. Conveniently, after paying waaaay too much and borrowing even more to buy it, I found out that it may have been THE worst vehicle F#$% ever put on the road. All kinds of bad design. Anyways, I have timing chains ready to let go at 145,000 miles, bad 4wd control module, in-op rear a/c, just replaced trans and converter $2400 etc etc

I am getting rid of it, and trying to be smarter about what I choose. I've wound up completely stuck and stumped on this, and can't find the info I feel like I need.

Supposedly there are 2 RPO codes for what I will call "not open" differentials. One is supposed to be a speed sensing automatic locking type (G80 eaton gov-lock), and the other an actual "posi" (G86 eaton clutch style).

Now, what I understand is that G80 only represents an option, which would be specific to that year or generation of model. Meaning that G80 doesn't designate one exact/specific "not open" carrier, it designates the model GM was using for that truck, in that year model. I may have concluded that G80 in trucks means auto-locking differential, but until 88 or so, was a torsen (torque sensing cone-style autolocker that would burn up), and then was changed for the eaton speed sensing gov-lock (known on the truck forums as he gov-bomb) up until about 06 or so. The cone auto lock turns into an open carrier when it burns up, and the gov-lock either breaks apart or seizes.

Supposedly this eaton unit blows up at will, because of its design. It has to sense 100 rpm difference in axle speed, then locks them until wheel speed reaches 20-25 mph. I've seen lots of pictures/read accounts of them grenading and taking out housings, gas tanks, etc. just from everyday use...like soccer mom everyday use. People say they'll never buy one again, rather have a peg leg than that thing. I've also read where people put 200,000 miles on them with no problem, towing, wheeling, working, hauling, etc.

The G86 clutch style option seems to be a LOT harder to come by, I even read that ALL pickups and sport utilitys that didn't have peg legs came with G80 auto lock differentials. I must have looked in the glove box of a dozen yesterday and they all had open carriers or G80 carriers.

I'm looking at a 99 tahoe 4wd and a 96 suburban 4wd, both priced where I can get them. The tahoe is a 350cid pushbutton 4wd and has a G80 186,000 miles rebuilt trans with vette servo. The suburban is a 350cid shift-on-the-fly 4wd with open rear end.

What kind of insight can you provide?
Is it true that all front differentials in GM trucks are open?
Have you had a good experience or bad?
Can you tell me what I should do here?
Will I be ok buying a G80 equipped vehicle, or just plain STUPID?

I need some help. Thanks!!!!!