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Discussion Starter · #1 ·
Well here I am again asking questions.

So I replaced the driver side valve cover and the oil burning stopped, and was driving the truck around again when I had to use 4WD no big deal the truck was running fine and the 4WD worked great but then I switched back into 2WD and the truck started randomly jerking and slamming when driving down the road, I started watching the spedo and tach and noticed that the speed would jump when it did that but the RPM's didn't change so that ruled out the trans or transfer case in my book so I tore apart the rear diff and found the driver side spider gear mostly flat (I will attach photo if I can).

But I also noticed that the rear diff was an open diff not a gov loc. then I rechecked the RPO codes in the glove box and it said it was supposed to have a GT4, G80, and the gov loc is supposed to be a c-clip axle and the open diff axle is supposed to be attached behind the wheel backing plate, so I am wondering if there is a stamping on the housing that will tell me if I have to change housing to get it to be a gov loc again or if I can just use the current housing and put the correct carrier back in it? (and yes before people suggest it I know I can upgrade to a better carrier but it is a going to be used for street nothing extreme)

Also I can't tell if this current diff has c-clips or not.
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Thanks

Todd
 

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2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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My truck was like that as well (has the G80 code, but when I pulled the cover it was an open diff). Most likely the G80 failed for a previous owner, and they just put in an open diff because it was cheaper and less likely to fail.
 

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Any idea what caused that nasty detonation? Had you ever changed that gear oil or is it just the photo's color wash with the flash? Looks like chocolate milk.
 

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I would consider an aftermarket posi unit instead of a replacement G80.
 

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2003 Silverado 1500 LS
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Any idea what caused that nasty detonation? ........
I would guess that the previous owner (or maybe the OP) beat the heck out of the truck. I agree with davester above, I betcha the G80 blew up and then they rebuilt with whatever was available, and then beat the truck some more. Also, I can see some of the wear patterns on the drive side of the ring gear, and they are NOT correct!

OP, that is a somewhat easy rebuild, but you need a few special tools and a fair bit of mechanical knowledge. Lots of YouTube vids are available to guide you through the process. If you are having to ask whether or not that is a c-clip assembly (it is), then I would hesitate to see you tackle the job.

I would take EVERYTHING out.... every seal, every bearing... then douche the Hell out of the interior of the case with lots of cleaners and rags, get every last bit of metal out of there. Order up all your new parts and carefully install. I would replace every moving part in that case, axle bearings, axle seals, pinion bearings, carrier bearings, ring, pinion, carrier assembly, everything.
 

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Discussion Starter · #7 ·
Thank you for all the replies, and yes that is the color of the fluid when I opened it up, I didn't take to long to inspect it when I had it open I was doing it on jack stands and not a lift and it was cold so I didn't spend much time on the ground, and with the pic I could not tell from the shot I took if it was indeed c-clips, I have done other rear end rebuilds before, this will be a spring project so it is not so damn cold.

For now I replaced the fluid and cleaned it as much as I could but it is parked for now and I am stuck driving the car for the winter.
 

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If it wasn't clear, yeah same housing, just need to replace the internals. The G80 is notorious for being junk. I know the yukon duragrip LSD has been on sale for a while around $300. Truetrac is about $550.

I do most of my new stuff from youtube videos, but I always check these guys out. Pretty sure it's in here, and I think these guys do some of the best repair videos anywhere.
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2021 GMC Sierra Denali CC 4WD Ultimate 6.2L
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Everyone bad mouths the Eaton G80 locker but every truck I have owned for the last 25 yrs had one and i never had any problems. Millions of GM trucks and suv;s vehicles have successfully used Eaton G80 Locker. It is an excellent product. Like anything, it can be misused and misrepresented and blamed for things that are not its fault. Over size tires and never changing the oem fluid being a big source reason for failure.
 

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2003 Silverado 1500 LS
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Everyone bad mouths the Eaton G80 locker but every truck I have owned for the last 25 yrs had one and i never had any problems. Millions of GM trucks and suv;s vehicles have successfully used Eaton G80 Locker. I.........
Yeah, but honestly, if you were the OP and doing a total soup-to-nuts rebuild, would you install a G80 versus a Truetrac or one of the other terrific aftermarket carriers? All the evidence seems to indicate that this particular differential does see it's fair share of abuse, LOL..... ;)
 

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2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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...it sounds more like a previous owner abused it, then put in an open diff somewhat less then great, and then worked that over before selling it on. The o.p. may or may not be using it hard, seems to be working on fixing it up so it runs well, rather than to just beat on it.

But, putting in new guts, the g80 is likely in the same price range as other lockers, so it would be wise to consider the differences between them and how the o.p. will use the truck. Might also consider getting a used g80 from a junkyard (or even the whole axle, still likely less than a new unit, and be faster/easier to install vs setting up a rear end if you haven't done it before).
 

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Discussion Starter · #12 ·
To be honest I had planed on getting a used g80 and getting new bearings, seals and just making sure it is adjusted correctly. the truck is used for hauling, towing and my winter truck it is not going to be an extreme use truck, it is for when the car is not an appropriate vehicle to use for the situation.
 
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