Thanks for the tips! Where can I find out my truck's spline count? And I also heard about the G80s blowing up... but that's from people doing too many burnouts on asphalt and high power race car applications too. I might look online for a G80 with a guarantee/return policy...
Oh and did anybody put a G80 in the front as well?

 

Here is a nice down and dirty write up from another forum found via

The marketing term "Gov-Lock” was originally introduced by GM in 1973 when the first "locking rear differentials” were introduced as a replacement for the dangerous positraction units, the Gov-Lock rear-ends were essentially a cross between a limited-slip and true locking rear differential utilizing clutches and plates that transferred torque to the rear wheels, the Gov-Locks were built by various manufacturers (none by Eaton) these differentials were notorious for failing (exploding), the Gov-lock rear ends were discontinued In the mid 80's due to their high failure rates.


GM then got with Eaton to develop a high quality mechanical auto-locking differential that is heavy-duty, GM dropped the use of the marketing name "Gov-Lock” and the RPO code "G80” was adopted as the new marketing name.


The Eaton locker does use clutches but only as part of the cam unit that engages the locking feature, the clutches do not transmit engine torque and for this reason the Eaton rear-ends do not fail and "explode” in the way the old GM Gov-Locks would.

The G80 is available in all GM light duty truck axles including the 8.6”, 9.5” and even the 10.5” axle which is used behind the 650ft/lb of torque Duramax engine.
Due to the nature in which trucks are used (and sometimes abused) the Eaton G80 units are not infallible but the failure rate is now very minimal in comparison.

The Eaton G80 is intended to benefit the average truck buyer by transmitting torque to both rear tires when wheel slippage occurs, this feature works well in instances where one tire is off the ground or on ice or other slippery surfaces but it is not always optimum for off road (4X4ing) use, many off-roaders prefer to have full manual control of their differential locking mechanism and to engage it prior to entering an area of poor traction and for these folks the G80 is not suitable.


sorry for the double post but this would have made the last un-readable due to length

 

As usual AB has hit the nail on the head. They are good units. I have had no trouble with mine. My Sonoma is a 94 but it has the 93 running gear in it. I dropped the G80 in mine with no trouble.

if your scared of them you can get locking diffs from summit racing.

 

Thanks! I think I might stick with the G80 since it's much cheaper than those other powertrax locking diffs. I don't wanna dump too much money in my truck for now (I have a 91 trans am convertible I'm working on). I could see why serious off-roaders might prefer something other than the G80 but for the off-roading that I do, a G80 should be a BIG help, especially after getting stuck in this and helplessly watching only the 2 wheels without traction spinning:



And would it be a bad idea to use the G80 as a front diff too?

 

I remember that pic!

I have asked that question in another thread. I'm gonna put one in my Sonoma and see how long it lasts.

 

Hahaha yep! I posted up a thread about a month ago about this situation (i think i called it "last time i'm EVER doing this alone again" or something like that)

 

i'm surprised that no one has mentioned this yet.........

"It will fit any GM vehicle with 8.5 rear / 30 spline axles 1989 thru 1998. Fits half ton trucks, Suburban, Van, and most rear wheel drive cars. This will also fit GM full size 4 X 4 solid 10 bolt 8.5 front axles 1989 thru 1991"

this will NOT fir our trucks-the S seris have 7 5/8 diff's, not the 8 1/2.

i've put Auburn posi units in before, never had any issues with them-and i'm overly hard on my trucks.

 

This one here on Ebay is not a bad deal and will fit the S-series trucks.

http://cgi.ebay.com/ebaymotors/GM-7-...item2ea9a64afe

 

They definatly make the G80 for 88 and earlier 7.5 26 spline and 88 and later 7.625 28 spline differentials and in the midsize blazers and s-10's the front differential is a 7.25 IFS witch means they dont make a G80 for the front you can buy a powertrax lock right for the front but if you want to be able to steer when in 4x4 in the throttle and avoid striping the teeth off the front axle engagement connector and sleeve its not for you.