G80 ready to blow up?

[BMarino]

Yesterday, as I was taking off from having been parked at the side of the road, I'd advanced at a slow speed at most 10 meters when suddenly and with a very loud CLUNK, I lost power to the rear wheels. I thought the U joint had tore apart. But I soon found out that was not the case.

As cars were approaching behind me, and apparently there was still some power left, I gently but steadily continued accelerating in order to get to the side of the road, but as I did this, it became clear the driver's side rear wheel was locked up and only the passenger side rear wheel had free movement.

I managed to get the truck out of the way by advancing slowly and dragging the locked up tire, and as soon as I completely stopped, another CLUNK was heard and all returned to normal. This sound was however different from the first, it was as the one heard when putting the gear selector out of parking and into drive when truck has been parked on an incline.

Truck (1997 K1500) has the 4l60e transmission, 10 bolt - 3.46 gear ratio - G80 limited slip rear differential. Parking brake is disconnected. Rear drum brakes were looking ok when I inspected them a few months ago.

I care for this truck, it's my daily and use it thoroughly on highway use, offroad (forest service roads) and towing within its limitations say once a month.

I'm at a loss on what could have happened to cause this. I need to be sure what was it as I can't have this happen at high speeds on the highway as that would be damn mayhem.

I actually was planning on very soon doing a diff oil change, as that's the only fluid replacement I haven't done on this truck since I bought it 1.5 year ago (I did inspect the fluid soon after getting the truck), so I'll be doing this and taking a look inside the diff.

But I think it all inside there should be fine. I mean, after this incident, I drove around 60 miles at highway speed and around town with no issue whatsoever. If something did break, I wouldn't expect to even be able to drive it anymore.

Can anyone give me a hint on what could've been the issue here?


Thanks folks!

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[CumminsFever]

My 1st thought: the brake lining sheared off the shoes on left rear side. It's in there doing funky things. When you stopped, the truck went backward just far enuff that it released, allowing "normal" operation.
I'd check the brake 1st.

 

[GrimsterGMC]

Maybe a wheel bearing, if a ball or roller cracks through the middle it can stay aligned together as one piece for ages, then for no reason rotate like a sprag clutch and lock the axle up but removing the load allowed for it to realign and you were able to continue.

 

[GoToGuy]

Something unusual, unknown caused a potential catastrophic incident, and you didn't decide to return home and pull the rear wheels, drums, and diff's cover ? What's Murphy's Law on knowledge of something wrong but ignoring a problem waiting to happen?
The correct answer is " check and inspect ".

 

[Schurkey]

Perhaps a moderator will move this out of "Transmissions" and into "Axles + Brakes".

My experience has been that if a G80 is going to blow up, you don't drive it for another sixty miles. You skid to a stop, and then the tow-truck hauls it away.

I've seen multiple vehicles where the brake lining separates from the shoe, and causes all sorts of locking-wheel problems that come and go.

 

[BeardBoys9004]

From experience two weeks ago....my son was driving my hunting truck, 99 GMC Sierra 4x4 (New bodystyle) with 3.73 gears. So basically a 2000 because not one part on this vehicle thats been replaced has been for a 1999 . He called me saying it had made a loud clunk and was now locked up on the highway!! Somehow managed to get over off shoulder of road. Someone had stopped before I could get there and told him to put it in reverse and back in drive. It then made another loud clunk. Dude told him to drive around parking lot. He takes off and scatters something in the rearend. That in turn, knocks a chunk out of the housing, metal is clunking around broken and oil is going everywhere. Im thinking probably spider gears and everything in trashed from looks of things. Wrecker it home and get the housing off and it was the carrier but still definitely fubar'd!! Gears and all still look good but dont know til its taken compleyely apart. Alot of money to fix so looking for a whole rear axle to replace it. As this seems to be the best option now. If he'd waited and not driven it again we wouldnt be in the situation. We couldve put it on a rollback and saved the housing and possibly the carrier as well. Hoping you got yours checked out and all is well now

 

[jd33173]

From experience two weeks ago....my son was driving my hunting truck, 99 GMC Sierra 4x4 (New bodystyle) with 3.73 gears. So basically a 2000 because not one part on this vehicle thats been replaced has been for a 1999 . He called me saying it had made a loud clunk and was now locked up on the highway!! Somehow managed to get over off shoulder of road. Someone had stopped before I could get there and told him to put it in reverse and back in drive. It then made another loud clunk. Dude told him to drive around parking lot. He takes off and scatters something in the rearend. That in turn, knocks a chunk out of the housing, metal is clunking around broken and oil is going everywhere. Im thinking probably spider gears and everything in trashed from looks of things. Wrecker it home and get the housing off and it was the carrier but still definitely fubar'd!! Gears and all still look good but dont know til its taken compleyely apart. Alot of money to fix so looking for a whole rear axle to replace it. As this seems to be the best option now. If he'd waited and not driven it again we wouldnt be in the situation. We couldve put it on a rollback and saved the housing and possibly the carrier as well. Hoping you got yours checked out and all is well now

Brutal!

 

[movietvet]

Hard to believe you drove 60 miles with the rear diff grenading. With all that happening, I would have had towed till inspected.

 

[Schurkey]

Wow. ANOTHER "Ten Bolt" that exploded during normal use. This should be a surprise...but it isn't. Consider yourself lucky that it didn't lock-up at highway speed, leaving the rear tires skidding and out-of-control.

Guys think I'm extreme for suggesting people get rid of them at the first sign of trouble.

If they need fresh gear lube, they're totaled and should be replaced with a "14-bolt" semi-float 9.5" axle, which--in most cases--comes with the 11.x Duo-Servo brakes as a bonus upgrade for those craptastic 254mm Leading-Trailing shoe drums on almost all the "10-bolt" axles. (Some "10 bolt" axles especially in the SUVs have decent brakes. Most don't.)