Topic: Differential information

[ckrummy]

I really feel stupid for asking but just can't find the information out their, I have a 2002 Avalanche z71 160k miles. I recently took it off roading and found myself in a twist ditch type situation  and couldn't go through it i had to change my line, one of my co workers said that all z71 trucks have locking front and rear differentials and that something was wrong with my truck causing it now to work, he pointed out that it could be an abs sensor, which would make sense because my lights on.  I guess i don't know how gm's lockers, or even the front differential works, i know theirs a collar that locks the right axle together to engage 4wd, but do they use a limited slip, open, or solid differential in the front.

[oHIobellboy]

Front end is NOT a locker. I've been in soft wet grass before and the front drivers tire would not "drive" so to speak. Basically a 3 wheel drive.

[Main One]

Tell your coworker that GM sold some trucks (not any Avalanches to my knowledge) with the Z71 package that weren't even 4x4.   

[AvalancheAviator]

There is a chance that your diff isn't limited slip at all. I say this because mine has the "one wheel squeal" 

Seems like the Z71 package should include limited slip....

[HenryJ]

Nothing in the ABS system will affect the locking differential. Many were equipped with the Eaton Gov-loc differential.
This differential locks when one wheel spins and engages the drive mechanism. With enough force the clutch pack is engaged. The clutch engages and locks the two axle shafts to propel the vehicle. It will not engage at speeds above 25 mph. Fly weights prevent the mechanism from locking.
Here is a video of the Eaton differential:

Inside the Eaton G80 Locker

Inside the glove box there is a sticker with three digit codes. These are the RPO (Regular Production Option) codes. Codes with the letter G are differential codes. The Eaton Gov-Loc differential is listed as G80

[Main One]

To my knowledge, all GM Z71 packages included a locking rear diff, usually if not always the G80, whether 2x4 or 4x4.  The 2-wheel drive Z66 package also included the G80.  I'm also under the impression that in Avalanches GM didn't offer a locking front diff from the factory, but I could be wrong about that.

While at the Hot Rod Power Tour stop near St. Louis a couple of weeks ago, I chatted with a couple of Eaton reps, mostly about the Eaton Detroit True Track differential I just had put in, but also I told them it was replacing a quite cracked G80 with close to 250,000 miles on it.  They were a bit surprised that it lasted that long.  They indicated they were usually good for 150,000 or so miles.

[HenryJ]

... I told them it was replacing a quite cracked G80 with close to 250,000 miles on it.  They were a bit surprised that it lasted that long.  They indicated they were usually good for 150,000 or so miles.

Meh, I have three in the fleet at or past the 200k mark still going strong. I have had many more failures in the open differentials due to the poor side gears. It took me a while to figure out it was a better investment to replace the carrier with a used G80, rather than replace the crappy side gears and spiders.

[Main One]

Meh, I have three in the fleet at or past the 200k mark still going strong. I have had many more failures in the open differentials due to the poor side gears. It took me a while to figure out it was a better investment to replace the carrier with a used G80, rather than replace the crappy side gears and spiders.

They may have "derated" it some for the typical Hot Rod Power Tour guy.  I also may have mentioned something about it outlasting a rebuilt tranny that had its output shaft shattered due to shifting so hard on the 1-2 on the throttle, running a supercharger, and who know what else.....

[ckrummy]

  Ok i just took a look and it does in fact have a G80, could they fail from worn out clutches. and i also notice that my cover is leaking slightly, do those differentials call for LSD additive?

[Main One]

The covers corrode over time and start to leak.  I just put a new one on Saturday.  About $35 at NAPA.  About $65 with 3 quarts of lube.

[oHIobellboy]

Ok i just took a look and it does in fact have a G80, could they fail from worn out clutches. and i also notice that my cover is leaking slightly, do those differentials call for LSD additive?

Use Mobile1 and you don't need any additives. You can order a Chrome cover from Summit for around $30 that has a magnet and a drain plug in it. It's best to call the dealer with you're VIN to find out EXACTLY how wide your housing is. It can make a difference.