Its a 2008 Silverado 2WD 2500HD. I don't even know what the rearend is they put in these things, but I need a limited slip of some kind. Better to buy a diff and install or buy a new rear axle with the LSD already in it? I can do the first, but probably prefer the second as I figure it would be less work, but could go either way. I need to make this happen with as little cost and effort as possible. What say you? Oh, and no cracks about drugs. Not cool. 
JY full rear. Bolt-in from the same type of vehicle.
Stamps. They are easy to hide or explain if they are found.
P.S. I see what you did there in that last sentence.
Go to the college chemistry lab. They can make it for you. 
Now, after reading the post, go with a junkyard rear assembly.
NGTD wrote: JY full rear. Bolt-in from the same type of vehicle.
JY? Is that the type of rear it has?
JY stands for Junk Yard I believe.
How much real estate do you have on the side?
In reply to wvumtnbkr:
Yes, that would make sense.
wvumtnbkr wrote: JY stands for Junk Yard I believe.
Bingo, and just find one with the same model and similar year to your truck. Do your research and know what exactly you are looking for. If LSD wasn't offered in your gearing option, buy a LSD rear from the junk yard and swap just the differentials.
It probably has a 14 bolt rear. Some came with LSD, some came with an automatic locker. Mine in theory is the auto locker version, but I'm not convinced.
After having played around in an XJ with a lunchbox locker, that's what I'd probably go with. That thing was impressive in the dirt, and not too cumbersome on asphalt.
Normally I'm all about replacing the whole assembly versus messing with gears, but be aware that a 14 bolt is HEAVY.
In reply to DILYSI Dave:
Well now that you mention that let me ask you a question. What is the difference between LSD and automatic locker? When I bought it I was convinced it had a LSD. I based that on its driving characteristics, meaning that it acted like a LSD, seeming to put down power to both rear wheels when needed. But the first time I had it jacked up I notice that when the trans was in park the tires rotate in opposite directions, which at least with the traditional style diffs indicated it was open. I'm not sure what the distinction is between an LSD and and automatic locker, I thought I would ask. Is that still the case? BTW, I just took a 14 bolt out of my '78 dually, and know exactly how heavy it is! 
Jello Biafra said: I do my part Behind the lines Swabbing door handles of cop cars With D.M.S.O. Mixed with L.S.D.....
Look for RPO code G80 on the card in the glove box. That's the code for locking rear axle.
I'd mix it in with the differential fluid.
In reply to drummerfromdefleopard:
Another one that doesn't read...
Figure out if you have the Corporate 14 bolt rear, or the AAM 11.5 rear. Look at the diff covers here to compare, pretty obvious.
http://www.ringpinion.com/b2c/DiffList.aspx?SearchMode=Make&MakeID=3&ModelID=467&Side=Rear&DriveType=4WD
Replacing just a carrier is not very hard. The hardest/most time consuming part in setting up gears is setting the pinion depth. The pinion won't get screwed with since you're not changing ratios.
Changing the carrier will basically consist of removing the axle shafts(super easy if they are full floating), pull diff cover, use dial indicator to figure out how much backlash exists with gearset(you want to replicate this same number later so the gears aren't wearing on new spots), unbolt carrier and remove(can be a pain in the ass if there is lots of preload but usually not too downright horrible).
If you have the AAM 11.5 it's dead easy as they have threaded adjusters which you use to tighten each side of the carrier, changing how much it is left vs right will move it around left to right to change backlash, increasing both increases preload.
The GM 10.5 14 bolt also has threaded preload adjusters which are awesome.
You swap the ring gear over, and bearings too(or put new ones on, may as well), reset the backlash to spec while making sure preload is sufficient. With shimmed axles, it's pretty damn hard to give too much preload unless you're using a housing spreader(I never use unless ABSOLUTELY needed, it is very easy to wreck a good housing with one used improperly). With the threaded adjusters, basically gauge how much effort it took to undo them in the first place. As long as you're not going apeE36 M3 on them you'll be fine.
edit: Here is a post taken from a D44 regearing how to I did years ago. This is essentially what you'd be doing, except the 14b and the AAM 11.5 both have threaded preload adjusters so it will be 10x easier with no special puller needed for putting bearings on and off.
http://www.jeepforum.com/forum/f19/regearing-marinejrms-xj-d44-992471/#post9095545
Where I'm making shim changes which take 5+min each time.. you're just turning threaded adjusters one way or the other to add preload and/or move the carrier left or right.
my 2010 1500 had the Elock diff. when you get going around 20 mph you'll hear it click audibly as it locks the diff.
You confuse "not reading" with "not giving up a joke opportunity"
Just one "an" in the thread title would've prevented all this
The G80 locker uses speed difference of left vs right before it locks up completely. It will act like an open diff until then.
Jack one rear wheel in the air and put it in neutral. Then manually spin the tire as fast as you can. You should be able to do it fast enough to get the fly weights to push outwards and cause it to lock if it has the G80 "gov locker" diff.
Also google "gov-bomb differential" they had a tendency to grenade if you do one wheel peels or drive aggressively on muddy terrain often. More common in the lighter duty G80 optioned 1/2 ton trucks though still happens in the big stuff.
I was going to say 'trans has to be in neutral, not park', but flatlander got it for me.
I have heard that some street stock racers run very thick oil in an open differential to get more bite. Let me know if it works because I am curious but not so much that I plan to try it.
The gov-lock diffs are made for low speed, crawl out of the ditch type stuff. Use it like a sportscar and you'll kill it. A used diff may be worn out when you get it. A rebuild maybe just a costly as a new one. Powertrax has a system that bolts into the exixting carrier without having to play with the ring and pinion settings. I have no idea of it's any good, but its another option.
gov locks work well for truck work. i rarely used 4 wheel drive in the avalanche in mud.
if you have a 14 bolt and a 1996 diff will work, i have a drum to drum 3.73 g80 locker from a 96 burb sitting here that you can have cheap. worked fine, was just a street driven truck, i parted it for body panels.
I don't have much to add other than watching with interest.
Its got the G80 code, which explains why it drove like it had a posi. Thanks for all the information, guys!
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