Gov loc differential???

[Matt69olds]

Did some routine maintenance on my sons 92 Yukon, noticed the rear tires turn opposite from each other when rotated by hand. Classic example of a open rearend. However, the RPO code shows G80 which is locking differential. If I remember correctly, these trucks have the dreaded Gov-bomb diffs. Has this one already exploded? Or does it take a certain amount of slip for the diff to lock?

Is there a better junkyard diff that will bolt into this rearend? This is a half ton Yukon, I assume it’s the common 8.5 rear that other half ton trucks use.

My son has big dreams for this truck, just as we all did with our first car/truck. I’m trying to drill into his head the lowbuck but do it right mentality. In other words, build the truck the right way, but as cheaply as possible.

 

[yevgenievich]

It locks when the speed difference is reached. Gov lock always worked fine for my use, but smallest diff I had with a government lock was 9.5". Gov lock does not like high speed wheel spin with sudden traction catches.
9.5" diff from a light duty 2500 truck would swap in.( keeps it 6 lug)

 

[bucket]

I agree with swapping in a 6-lug 14 bolt axle if durability is concerned. However, the Gov-Loc in the 9.5" diff is also rather fragile, much like the 8.5" diff. Just not AS fragile.

But, the stock unit may not be busted yet. It would be good to pull the cover for a look-see.

 

[wlwarnke]

G80 functions like an open diff until 100rpm delta between axles. Then locks. Supposed to unlock at approx 20 mph.

They are not high speed burnout devices because of the 20 mph limit. This is how people destroy them. They are for low speed use.

They can be modified to defeat to 20 mph limit however.

 

[Catbox]

Gov-Bomb.
This is what my first one did to itself.
The suburban is my wife's grocery getter, no offroad pretty much at all with it since we have had it.
We were on the way to a hockey game and making a left turn when the whole rear end jumped and made a wicked popping sound. I put it into 4wd and limped into the parking lot.

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The rearend is not something I would cheap out on.
I tried that with a second hand carrier from the junkyard to replace this one.
We were not financially positioned to do a full boogie rebuild back then.

It lasted about 2 years before I was into the rearend again.
That is when I put in a whole new set up with a Detriot True trac.

 

[skysurfer]

Epic carnage pics Cat.

 

[shiftpro]

My AWD Astro van had one. It worked good for getting out of my snowed in back alley, turning out of my carport and going up a slight hill. I could hear and feel it kicking in. How many times can that thing go 'thump' before it changes it tone to 'snap'?

 

[dvdswan]

Gov-Bomb.
This is what my first one did to itself.
The suburban is my wife's grocery getter, no offroad pretty much at all with it since we have had it.
We were on the way to a hockey game and making a left turn when the whole rear end jumped and made a wicked popping sound. I put it into 4wd and limped into the parking lot.

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The rearend is not something I would cheap out on.
I tried that with a second hand carrier from the junkyard to replace this one.
We were not financially positioned to do a full boogie rebuild back then.

It lasted about 2 years before I was into the rearend again.
That is when I put in a whole new set up with a Detriot True trac.

This is why potty training is important... Nobody needs to see that. LOL

 

[SquareRoot]

A similar conversation came up on another site. I noted that my 21 Canyon Duramax AT4 comes with the G80 "locking differential". It was odd to think GM would still be using the design if it was such a POS over all these years. I'm "told" that the G80 is just the RPO code and has never changed. However, what was called the Gov Bomb is a far different design than the G80 in modern trucks. I don't know if that's accurate but that's what they say. Maybe @Keith Seymore would have some insight?

 

[Bextreme04]

A similar conversation came up on another site. I noted that my 21 Canyon Duramax AT4 comes with the G80 "locking differential". It was odd to think GM would still be using the design if it was such a POS over all these years. I'm "told" that the G80 is just the RPO code and has never changed. However, what was called the Gov Bomb is a far different design than the G80 in modern trucks. I don't know if that's accurate but that's what they say. Maybe @Keith Seymore would have some insight?

G80 is the RPO for "locking diff" but they are all very similar. As far as I know they are all designed by Eaton and share much of the same design. The one in my 2011 Suburban 8.6" looks identical to the one @Vbb199 had in his 10 bolt suburban rear end. It's going on 208,000 miles and has never given me any noise or issues. Snow, rain, ice, mud, towing, etc.... I just inspected the Eaton unit, cleaned it all up, new bearings and 4.10 gears and it's back on the road.

Its probably the same one @Catbox had in his also. The CUCV's all got Detroit lockers in their 14BFF.

 

[Catbox]

Epic carnage pics Cat.

Yup.
I blew the junkyard Gov-Bomb unit in a similar fashion.
At that time I had just gotten a bonus check from work and we had it towed to the local guru.
I had the whole thing rebuilt at the time with a Detroit True Trac, ring & pinion, and an axle.

Make sure you keep an eye on the axle bearing wear surfaces as well.
Once you have worn through the hardened part, they need to be replaced before failure.

The True Trac lasted us for 5 years.
I believe we had a bent axle tube from a tire coming off at about 30 mph that put some stress on the parts inside the diff that caused its failure. It took a couple of years, but I felt the same popping feeling from the rear of the sub.

Off to the shop again, this time my old guy retired so I found a new one through a racers page on facebook.

Now we are a Yukon Dura Grip kinda family.
It seems to work like a champ.
That one has been in there for almost a year now and has been trouble free.

 

[77 K20]

I had a 1998 ZR2 that had the G80 from the factory in the rear axle. At times it would engage rather rough but never had issues with it offroading. It was only on 31" tires. I was on a ZR2 forum back then and failures were not that common unless someone was doing something very stupid.
I had a 2003 Silverado with the 6 speed manual and the 8.1L engine. It never clunked/slammed like the ZR2 one did and yet it would still lock the tires together. I had 285/75R16 tires on it and had lit them up on more than one occasion.
Just seems to be how lucky you are I guess.

 

[Rusty Nail]

They require maintenance... I always use a bottle of positrac additive. IDGAF what the GL5 label claims. Cones with it you say? Yeah. As soon as I put it in there it'll have some.

I could add some bull stuff story about the 8.5" in my SS but why bother? Chirps third at 85 and never complained.

This dude blew his schitt up in a parking lot. :smh:

Change the fluid ffs. That interval is 30k. Add the little bottle.
Go head and take the cover off and hose down the guts with brakeleen.

Undeserved bad rap.

 

[gmbellew]

I rock them until they go. I have an 04 burb with 250k on it and still works great. the 90 burb blew it out at 200k and I replaced it with a truetrac. I am not rough on them. if you are rough on them, they don't seem to last very long....

 

[Rusty Nail]

My AWD Astro van had one. It worked good for getting out of my snowed in back alley, turning out of my carport and going up a slight hill. I could hear and feel it kicking in. How many times can that thing go 'thump' before it changes it tone to 'snap'?

I wish I had an AWD Badasstro van.
You could get one with a 4.3L OR a freaking IRON DUKE!
/pwncity

I'd jack it up and run big ash ATs on it so fast it would make your head spin.

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