G80 possible issue

[kbuskill]

Ok, so today I went out to do a couple of test passes on the Burb to get some baseline data from the Torque Pro app before I get the headers put on so I can compare before and after numbers.

My plan was to do 3 test passes from 0-100 and then average those to get the baseline.

I got the app ready to record and turned OFF the A/C, Traction control, and Stabilitrac... this is the procedure that Lew from Diablew tuning told me to use when doing WOT logs.

I hammered it hard off the line and the right rear tire broke loose for a second and the the locker locked in and away I went... all the way up to 100mph.

I then slowed down to a normal speed and proceeded down the road a little ways until I could find a wide spot to turn around to go back and make another pass on the same stretch of road to keep the test consistent.

When I turned hard left to make the U turn I noticed that the locker was still locked... it was acting like a positrac and skipping the wheel.

I drove all the way back to where I started and made another left hand U turn and it did the same thing.

I then pulled onto the side of the road and put it in reverse and tapped the gas a little and proceeded to make another left handed U turn... still locked.

At this point I'm starting to think I broke it so I head back for civilization and go to a big parking lot so I can do some tight turns.

I got to the parking lot and turn left into it.. it still feels locked... the minute I started to turn right I felt/heard it unlock...

I made several tight left and right hand turns and it was fine... no more dragging wheel.


So at this point I am a little hesitant to go make any more test passes because I really don't want to blow the rear end up in this thing.

From the research I have done the G80 should lock if there is a 100rpm difference between the wheel speeds and unlock above 20mph.

What do you guys think???

Any of you have any similar experiences???

@swathdiver

 

[swathdiver]

Might be the governor or worn clutches. Check your email in a minute...

 

[kbuskill]

Might be the governor or worn clutches. Check your email in a minute...

I checked out your email... I appreciate it.

After reading the trouble shooting section it almost sounds like may be one of the spring clips for the governor's weights are weak and not pulling them in.

I don't really know. If it happens again I will try turning right sooner and see if it unlocks right away.

So do you think it would be safe to continue my testing?

 

[iamdub]

Classic hanging of the Gov-Bomb. If it were me, I'd continue the testing and try to keep it locked between runs. This way, it won't be locking, unlocking, locking, unlocking, etc. under hard throttle. It would actually help your tests be more consistent since wheel spin wouldn't be a factor. Hard throttle with it locked isn't gonna damage it. It's the hard and sudden locking under load that gets to them.

Now, as to what's causing it to hang, that's another subject and it sounds like you're already on it.

 

[kbuskill]

Classic hanging of the Gov-Bomb. If it were me, I'd continue the testing and try to keep it locked between runs. This way, it won't be locking, unlocking, locking, unlocking, etc. under hard throttle. It would actually help your tests be more consistent since wheel spin wouldn't be a factor. Hard throttle with it locked isn't gonna damage it. It's the hard and sudden locking under load that gets to them.

Now, as to what's causing it to hang, that's another subject and it sounds like you're already on it.

It's the first time I've had a "problem" with it.

The funny thing is I just changed the fluid in the stupid thing before we took our trip at Christmas.

Drained the old fluid out and looked it over... no real metal on the magnet... just normal stuff... didn't even smell bad like they normally do.

I refilled with Mobil 1 75w90 without any additional LS modifiers or anything.

Any way... I will try to do some more testing I guess. Hopefully it holds together.

I hate beating on a truck with 230k miles on it. Unfortunately I can't think of any other way to get consistent results for comparisons. And for tuning purposes it requires the WOT logs.

 

[iamdub]

...I refilled with Mobil 1 75w90 without any LS modifiers or anything.

I don't know what's in that Mobil1 gear oil, but I'm pretty sure the special additive the Gov-Bomb requires is only available in a separate bottle or premixed in the correct GM gear oil for it to operate properly. I'd verify and correct this first and ASAP.

 

[kbuskill]

I don't know what's in that Mobil1 gear oil, but I'm pretty sure the special additive the Gov-Bomb requires is only available in a separate bottle or premixed in the correct GM gear oil for it to operate properly. I'd verify and correct this first and ASAP.

That's the thing... it's not a limited slip differential so a friction modifier is not required and not recommended.

The LSD additive actually causes problems for the G80 due to it causing slipping in the clutch packs of the locker.

That is why I didn't buy/add anything else to it.

There is even a TSB telling dealers not to add the additive to the G80.

 

[swathdiver]

That's the thing... it's not a limited slip differential so a friction modifier is not required and not recommended.

The LSD additive actually causes problems for the G80 due to it causing slipping in the clutch packs of the locker.

That is why I didn't buy/add anything else to it.

There is even a TSB telling dealers not to add the additive to the G80.

The center section has both the functions of a locker and a limited slip. The friction modifiers are included in the factory gear oil (89021677) and that is why the extra bottles are not needed. My old bottles mentioned this but the new ones (88900401) do not.

If the Mobil One fluid does not have any in it, then I bet she'd work right with a couple of the little bottles of posi-lube added to it.

 

[Ilikemtb999]

I’d be worried about it letting go and taking out the housing, I’ve seen it on off-roaders spinning a tire and then it locking.


Time for an upgrade, I bought a Yukon gear posi unit for a decent price. A Detroit would be quite the upgrade.

 

[swathdiver]

I’d be worried about it letting go and taking out the housing, I’ve seen it on off-roaders spinning a tire and then it locking.


Time for an upgrade, I bought a Yukon gear posi unit for a decent price. A Detroit would be quite the upgrade.

When mine goes or there's money burning a hole in my pocket, I'm going AXN.

When the posi or locker portion breaks, it's designed to make a loud bang and then still lock up under low traction until you get it serviced.

 

[gooffeyguy]

Redline 75w90 gear oil has modifier already added into it also

2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18

 

[iamdub]

That's the thing... it's not a limited slip differential so a friction modifier is not required and not recommended.

The LSD additive actually causes problems for the G80 due to it causing slipping in the clutch packs of the locker.

That is why I didn't buy/add anything else to it.

There is even a TSB telling dealers not to add the additive to the G80.

I had to look that up and just ran across something I've never realized- The RPO "G80" is used for "Limited Slip Differential" as well as "Mechanical Locking Differential". Apparently, one got the friction modifier and the other didn't.

Learnt sumpin' new.

 

[swathdiver]

Well Ken, if your Mobil One bottle says LS on it, it has the friction modifier in it already.

 

[kbuskill]

I had to look that up and just ran across something I've never realized- The RPO "G80" is used for "Limited Slip Differential" as well as "Mechanical Locking Differential". Apparently, one got the friction modifier and the other didn't.

Learnt sumpin' new.

Yep G80 in the car applications is a LSD... G80 in a truck application is a locker.

 

[kbuskill]

Well Ken, if your Mobil One bottle says LS on it, it has the friction modifier in it already.

I will have to look at the bottle... I think I still have one.

I am certain it does though. Mobil 1's site shows the 75w90 as LS.

 

[swathdiver]

G80 in a truck application is a locker.

It's both a locker and a limited slip. According to GM, they've been using this since the 1980s.

 

[thompsoj22]

It's the first time I've had a "problem" with it.

The funny thing is I just changed the fluid in the stupid thing before we took our trip at Christmas.

Drained the old fluid out and looked it over... no real metal on the magnet... just normal stuff... didn't even smell bad like they normally do.

I refilled with Mobil 1 75w90 without any LS modifiers or anything.

Any way... I will try to do some more testing I guess. Hopefully it holds together.

I hate beating on a truck with 230k miles on it. Unfortunately I can't think of any other way to get consistent results for comparisons. And for tuning purposes it requires the WOT logs.

No offense but if your gonna play race car's with a 6k lb boat at least use some water to get the tires hot/sticky so you dont have spin on launch. your "limited slip" was designed for the occasional ice/snow/mud loss of traction and allmost requires a slippery surface to survive when it engages. the locking mechanisim might last for a couple more dry pavement burnouts and than there go's your headers in a diff replacement!. Forget the racetrack BS and do timed 10 mph rollon starts, it is more accurate in determining how your performance upgrades will get you up to speed on a freeway onramp as opposed to "launching" from a dead stop. No disrespect intended here as i see many of your posts and you know what your doing! no additive req in gov lock diff's so your fluid is irrelevant, it is just your gov lock screaming "im about to grenade"!

 

[kbuskill]

No offense but if your gonna play race car's with a 6k lb boat at least use some water to get the tires hot/sticky so you dont have spin on launch. your "limited slip" was designed for the occasional ice/snow/mud loss of traction and allmost requires a slippery surface to survive when it engages. the locking mechanisim might last for a couple more dry pavement burnouts and than there go's your headers in a diff replacement!. Forget the racetrack BS and do timed 10 mph rollon starts, it is more accurate in determining how your performance upgrades will get you up to speed on a freeway onramp as opposed to "launching" from a dead stop. No disrespect intended here as i see many of your posts and you know what your doing! no additive req in gov lock diff's so your fluid is irrelevant, it is just your gov lock screaming "im about to grenade"!

No offense taken. I agree, the 10mph roll is probably a better idea and definitely easier on the equipment.

 

[Ilikemtb999]

It's both a locker and a limited slip. According to GM, they've been using this since the 1980s.

Yep, and the one in my blazer is actually beefy and works well even off-road. 14 bolt axle is much larger.