That’s the one - they are great diffs.
You may notice a slight posi effect going around a tight corner with a little throttle but nothing that would bother ya.
CK5
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G80 not unlocking
- Thread starter ashman
- Start date
You may notice a slight posi effect going around a tight corner with a little throttle but nothing that would bother ya.
For what it’s worth the gov lock lasted 100k cool. The torsen in a buddies truck is nearing 700k miles and mine has 240k on it. I have personally seen ten units over 500k miles.
I decided to put in an offer on the one from ebay. Price is right and sounds like it's an upgrade.
Don't mess around with another G80. Get a Truetrac.It's an 11.5. So basically, I need to replace it.
Never tried to source a g80 before. Hope it's not too expensive. Ugh
My son's Dmax had the G80 lock up and do the spool trick. A few weeks after we installed the Truetrac, he commented that he should have done it sooner.
Not sure what the problem is, you got a free locker. 
Aaah, the ol’ tombstone…
Ok, so I'm freaking stumpted again. I just got through installing the torsion style limited slip. Took the truck out for a test drive and it is behaving EXACTLY the same as it was. Rear tires are locked together under any turn at all, forward or backward.
Since I have an entirely different carrier, that can't be the issue. What the hell else could it be?!?
For reference, this is a 2017 GMC Sierra 2500HD with a duramax. Pretty much only been used as a tow rig. No warning lights are on.
Since I have an entirely different carrier, that can't be the issue. What the hell else could it be?!?
For reference, this is a 2017 GMC Sierra 2500HD with a duramax. Pretty much only been used as a tow rig. No warning lights are on.
Can you get a video of the truck going very slow ( like backing out of a driveway onto the street ) and another of turning on a street corner and finally doing a few slow figure eights in a big parking lot.
This may help with pinpointing the true issue.
Welp, I figured it out... and I feel dumb.
Turns out it was just stuck in 4x4 the whole time. I'm still unclear on why being in 4wd would cause the rear tires to lock together, but that was the issue.
After posting above, I did a little more google-fu and found an old forum post on a Duramax page that discribed my symptoms perfectly. Someone suggested that the problem was that it was stuck in 4wd. Seemed silly to me, but I decided to check.
First thing I did was put the truck in Neutral and let it coast down a hill. As soon as I turned the wheel (either direction), it would damn near come to a stop because the rear axle was locked together. Same thing in drive, or reverse. After that, I climbed under the truck to try and turn the front driveshaft, and it was definetly engaged. Dash indicated that it was in 2wd, so for some reason it was stuck.
I parked in a gutter, shifted the truck into Neutral again, then climbed out and was able to spin the front driveshaft, confirming the issue. I spun it back and forth a bunch, then put it back into park, and was able to confirm it was now in 2wd.
After that, no more diff lock up! The problem is fixed. I still don't understand how being in 4wd would lockup the rear axle, but that is what was happening.
It sucks that I spent $500 on changing out a perfectly fine g80 gov-lok, but at least the issue is resolved.
BTW, I have a known-good g80 for sale if anyone needs it.
Turns out it was just stuck in 4x4 the whole time. I'm still unclear on why being in 4wd would cause the rear tires to lock together, but that was the issue.
After posting above, I did a little more google-fu and found an old forum post on a Duramax page that discribed my symptoms perfectly. Someone suggested that the problem was that it was stuck in 4wd. Seemed silly to me, but I decided to check.
First thing I did was put the truck in Neutral and let it coast down a hill. As soon as I turned the wheel (either direction), it would damn near come to a stop because the rear axle was locked together. Same thing in drive, or reverse. After that, I climbed under the truck to try and turn the front driveshaft, and it was definetly engaged. Dash indicated that it was in 2wd, so for some reason it was stuck.
I parked in a gutter, shifted the truck into Neutral again, then climbed out and was able to spin the front driveshaft, confirming the issue. I spun it back and forth a bunch, then put it back into park, and was able to confirm it was now in 2wd.
After that, no more diff lock up! The problem is fixed. I still don't understand how being in 4wd would lockup the rear axle, but that is what was happening.
It sucks that I spent $500 on changing out a perfectly fine g80 gov-lok, but at least the issue is resolved.
BTW, I have a known-good g80 for sale if anyone needs it.
My guess is that the rear isn't actually locked up, it's just the easier end to release the stress of the different wheel speed. (Unless loaded with weight in the bed.)
And the rear needs some decent "differential " action with the length of the truck.
So it pushed the stored energy out into a rear tire.
And the rear needs some decent "differential " action with the length of the truck.
So it pushed the stored energy out into a rear tire.
My guess is that the rear isn't actually locked up, it's just the easier end to release the stress of the different wheel speed. (Unless loaded with weight in the bed.)
And the rear needs some decent "differential " action with the length of the truck.
So it pushed the stored energy out into a rear tire.
That sounds like some of my previous diagnostic episodes right there.
