G80 go BOOM

[Wells596]

2005 Tahoe Z71 Alright as the title suggests my G80 decided to grenade itself. I finally got around to fixing the rest of the issues on this thing after letting it sit for a year in the driveway. Drove it to the job site with no noise whatsoever, went to leave and all of a sudden it acted like the diff was locked. Kept going and eventually it stopped, pulled into the courthouse parking lot to go renew tags and the whole truck just jerked all over. Get to my house, which is right around the corner from where I was and then it grenades completely. Now here’s the question, what’s a bolt up replacement that’s better than what came in it? I’d rather just bolt up a newer rear end and modify some stuff if needed so I don’t need to worry again. I know people will say put an Eaton or Detroit in it but with how cheap I can get a complete rear end I’d rather go that route. Debated putting a mini spool in but worried about snapping an axle.

 

[Wells596]

I guess I should add that what I meant by it feeling locked was that it had the locker engaged, not that it wouldn't move and I just forced it. lol

 

[6speedblazer]

Newer 2wd escalades came with the semi float 14 bolt axle. should be bolt in and go.

But honestly a 10 bolt with a truetrac is plenty strong.

 

[strutaeng]

Depends on what's available in the salvage yards nearby and how much you want to spend and your mechanical capabilities. We don't know this.

#1. Easiest/cheapest is probably another junkyard 10 bolt from the wrecking yard. Get a buddy to help you swap it, and can be done in a few hours. Just match the gear ratio from the donor.

#2. More expensive is a 14 bolt if you can find it as @6speedblazer mentioned. I guess it's the same work if they are a plug-n-play vs option #1? Will need a u-joint conversion but that's no big deal.

#3. Rebuilding your existing axle with an aftermarket differential? Assuming it can be rebuilt. Not sure how this compares to the others. You have to replace the ring/pinion, races/bearings, and do the tedious set-up and check for wear pattern and backlash/preload. Cost-wise, may be the most expensive option and take the longest, especially if you've never done this, although the work will be somewhat lighter, but repetitive and tedious. Will need a beam-style torque wrench that reads in in-lbs and a dial indicator guage that reads 0.001", besides other basic tools like an impact, torque wrench and bearing/race installer/remover.

Is the truck stock? No aftermarket lift or large tires? Was the differential ever serviced or any history with it? Was it beat on or abused? The G80 on my 99 Silverado 10 bolt is still going strong at like 285k. I've replaced the fluid a few times and have used it off-road a bit, but have never beat on it (except once I got stuck in the mud, LOL.)


Good luck!

 

[Doubeleive]

just throw a cheap used rear end on it then if that is what you can get, I have broke a few of those but i'm kind of a savage driver, under normal conditions it should be fine.

 

[Joseph Garcia]

^^^^^x2^^^^^ @strutaeng and @Doubeleive are spot on. As always, time and money are the determining factors.

You can have a used rear axle delivered to your door or shop from LKQ for less than $500, including freight (mine was less than $450, and it was a 14 bolt rear axle). And, you have some leeway in specifying the size (14 bolt versus 10 bolt) and mileage you want on the used axle from LKQ. I used them, and they were great. If you go with a 14 bolt, there are some restrictions on your donor truck options, and there may be a need for a converter universal joint, neither of which are big issues.

Now, in full transparency, I had a shop perform the work, and although the used axle was ready to install upon receipt from LKQ, I chose to have it completely rebuilt to have 4.10 gears (I had to do the same for the front differential, given that I was changing gear ratios), and I swapped out the G80 locker with an Eaton Detroit TrueTrac differential, based on the advice from the shop that rebuilt this rear axle for me.

One last point, if you are considering swapping out this rear axle yourself. These rear axles are HEAVY (at least, the 14 bolt rear axle was), and a forklift or other mobile powerful portable lifting device will be needed to remove it from the delivery truck. Two strong persons can barely lift one end of this rear axle.

Let us know what you decide to do.

 

[mikez71]

Agreed, that rear axle was heavier than I expected!
I thought two guys could lift it, but since I could hardly budge one end, I rolled out the cherry picker instead of calling anyone.

On another note, I've been doing 'burnouts' on wet weeds in the backyard.. Is that abusive to a G80?
(My mower isn't currently working, and just driving over the weeds doesn't keep it down for as long.)

 

[Marky Dissod]

... been doing 'burnouts' on wet weeds in the backyard. Is that abusive to a G80?

Cannot quantify HOW abusive it is, except to say that it'd be more abusive on grippier ground, but yes it is abusive. Think of it as accelerated wear.

 

[SpareParts]

It's the shock loading that does them in like doing burnouts in grass. Pavement kills em fast doing burnouts. 14 bolt G80's are the strongest from size alone.
4WD Suburbans can have 14 bolt SF in them also as i found out.

 

[mikez71]

So... new mower vs truetrac...
I do have a 14bolt G80. *Maybe* it can handle some grass?

@Wells596, did you notice any noises from the rearend prior to it grenading?
Because the wear looks like it had been going on for some time.. I bet the fluid looked great too..

 

[S33k3r]

Something MANY people forget on the G80s: there's a special additive that is supposed to be refreshed every 15k miles. If you don't keep on top of that, then your G80 will grenade. I have not heard of anyone grenading their G80s that kept up with that additive. YMMV

 

[swathdiver]

2005 Tahoe Z71 Alright as the title suggests my G80 decided to grenade itself. I finally got around to fixing the rest of the issues on this thing after letting it sit for a year in the driveway. Drove it to the job site with no noise whatsoever, went to leave and all of a sudden it acted like the diff was locked. Kept going and eventually it stopped, pulled into the courthouse parking lot to go renew tags and the whole truck just jerked all over. Get to my house, which is right around the corner from where I was and then it grenades completely. Now here’s the question, what’s a bolt up replacement that’s better than what came in it? I’d rather just bolt up a newer rear end and modify some stuff if needed so I don’t need to worry again. I know people will say put an Eaton or Detroit in it but with how cheap I can get a complete rear end I’d rather go that route. Debated putting a mini spool in but worried about snapping an axle.

There's nothing wrong with the design and yours did last 21 years or so. Metal fatigue and stuff just gets old and out of spec from wear and tear over time.

Get another from your generation to keep the track width the same and I think you might have traction control, so get the ones made for that feature.

A few years ago I bought a used differential for one of mine and zero timed it with all new parts, including the axle shafts.

 

[SpareParts]

Something MANY people forget on the G80s: there's a special additive that is supposed to be refreshed every 15k miles. If you don't keep on top of that, then your G80 will grenade. I have not heard of anyone grenading their G80s that kept up with that additive. YMMV

Can you show us where you got this info?

 

[SpareParts]

I think the problem is GM calls the Gov-Loc a G80 in trucks. The cars are also called G80 but are positrac and it requires the additive.

 

[West 1]

I think in your 2005 rear axle you will be limited to a 10 bolt. In 2005 the Denali and Escalade options advertised the rear axle was built heavier duty than the standard trucks. Maybe choose an escalade or Denali axle. Not sure what was changed in these axles but taking them apart the Denali axle was much tighter inside than a typical Tahoe axle. I would choose a quick bolt in replacement. Put new fluid in it and it will probably outlive your truck. A couple hours labor and you are back on the road.

 

[DaveO9]

^^^^^x2^^^^^ @strutaeng and @Doubeleive are spot on. As always, time and money are the determining factors.

You can have a used rear axle delivered to your door or shop from LKQ for less than $500, including freight (mine was less than $450, and it was a 14 bolt rear axle). And, you have some leeway in specifying the size (14 bolt versus 10 bolt) and mileage you want on the used axle from LKQ. I used them, and they were great. If you go with a 14 bolt, there are some restrictions on your donor truck options, and there may be a need for a converter universal joint, neither of which are big issues.

Now, in full transparency, I had a shop perform the work, and although the used axle was ready to install upon receipt from LKQ, I chose to have it completely rebuilt to have 4.10 gears (I had to do the same for the front differential, given that I was changing gear ratios), and I swapped out the G80 locker with an Eaton Detroit TrueTrac differential, based on the advice from the shop that rebuilt this rear axle for me.

One last point, if you are considering swapping out this rear axle yourself. These rear axles are HEAVY (at least, the 14 bolt rear axle was), and a forklift or other mobile powerful portable lifting device will be needed to remove it from the delivery truck. Two strong persons can barely lift one end of this rear axle.

Let us know what you decide to do.

on my '13 Tahoe I did the 14 bolt route and also used LKQ to source it. Also changed axle ratios at the same time - 3.08 to 3.42. (Front diff also sourced from LKQ). Happy with the results and would do it again. The only thing I will point out is LKQ requires a VIN when buying parts such as diffs, engines, trans, etc. And they are very strict with their warranties - if the parts you're buying do not match up exactly with your VIN, they will only sell those parts to you as-is, no warranty. Even a different axle ratio is enough to trigger this loophole. It's a risk I chose to accept. (Note that they still do allow returns within a short window, like a month. the initial 14 bolt I bought had some bent brackets and other issues that I didn't notice till I got it home. They did allow me to return and get a different one)

I found out yesterday that not all big salvage outfits do it that way. I bought an engine from B&R Auto wrecking, no VIN required, but with 6 month warranty.

 

[Marky Dissod]

LKQ requires a VIN when buying parts such as diffs, engines, trans, etc.

Wouldn't the solution here be to provide a VIN appropriate to the part you're asking for?

If you want to upgrade your Tahoe to H2 / 2500 parts, just provide the VIN for an H2 or a 2500 vehicle. Or am I missing something here?
(Building my spare VIN library ...)

 

[DaveO9]

Wouldn't the solution here be to provide a VIN appropriate to the part you're asking for?

If you want to upgrade your Tahoe to H2 / 2500 parts, just provide the VIN for an H2 or a 2500 vehicle. Or am I missing something here?
(Building my spare VIN library ...)

I’ve often wondered if you could do that. Use some random VIN like from a sale listing? Or a buddy’s rig that matches?

Theres more to my axle swap story. The first front diff I bought from LKQ had a bearing howl that I didn’t notice (or thought it was something else) until it was past the return period. When I eventually did decide it was bad and replace it, I did try to and make a claim with LKQ, even tried to see if they’d give me some consideration for a different unit. NOPE. Nada. I did buy another unit from LKQ, but this time I gave them the VIN from the 2009 Tahoe I had that was totaled a year or two prior. The 09 came factory with 3.42, and they accepted it. That unit has been fine tho, and I’m probably out of warranty period by now.

 

[S33k3r]

Can you show us where you got this info?

It's a friction modifier. If you buy the suggested/correct GM oil, it already has it. But here is where it talks about the friction modifier.:

G80 Gear Oil – The Ultimate Guide To Maintenance, Performance

I can't find the 15k recommendation, so either I am misremembering, or I'll post it later. I shall, however, mea culpa in advance.

 

[S33k3r]

It's a friction modifier. If you buy the suggested/correct GM oil, it already has it. But here is where it talks about the friction modifier.:

G80 Gear Oil – The Ultimate Guide To Maintenance, Performance

I can't find the 15k recommendation, so either I am misremembering, or I'll post it later. I shall, however, mea culpa in advance.

Hot damn! Apparently I was completely wrong:

Limited Slip Additive needed for G80?

Concerns about G80 rear diff - and gear oil question

GM Truck G80 Locking Rear End. Do I Need To Use LSD Additives In The Differential Oil?

Rear differential gear oil additive

G80 Rear Differential Fluid (GMT400)

G80 fluid type

Concerns about G80 rear diff - and gear oil question

G80 rear differential recommended fluid

My mistake is that I actually have at least three G86s, and possibly all five vehicles are G86. The wildcards are the Escalade and the 2005 Suburban 1500. Sorry for the confusion.