limited slip diff type?

[972sparky]

anyone know what the name of this type of limit slip diff is? I'd like to look into rebuild kits, like clutches and stuff. but never seen one like this?

any idea who makes it for gm?

Had one of these in a 2008 Avalanche, only had an axle seal go out due to the brakes overheating with a stuck piston otherwise no problems for 150K miles. Here is a rebuild writeup. https://offroadtb.com/rear-axle-g80-differential-rebuild/

 

[intheburbs]

The G80 is not "weak" and does not "break easily."

If you do stupid stuff - burnouts, donuts, etc - yes, it's more likely to break. If you drive with some modicum of maturity, it will outlast you. I have 3 G80 trucks with over 650,000 total miles and have had zero G80 issues.

 

[Fless]

It's very different, the AWD transfer case is like having a 3rd center section to prevent wheel hop.

When in Auto the front axle and driveshaft are engaged and turning but the computer is waiting to decide how much power to transfer from the back to the front.

This seems to be somewhat correct, although at what point does the front diff actuator couple the front propshaft (and transfer case) to the diff? It wouldn't be needed if they're already coupled. They are separate until the front diff actuator is commanded on.

At least that's the way mine is on my NP246 AUTO system -- I can tell when the front engages, maybe 1/2 second or so after sensing rear wheel slip. The T/C always keeps the front propshaft spinning at an appropriate speed so the engagement can be quick, but it's not coupled to the diff until the actuator, well, actuates it.

Obviously your newer systems might operate differently, but if there's a front diff actuator, I don't see how. Enlighten me, please.

Running in AUTO theoretically won't cause any additional wear on the diff, unless it's engaged by the computer. Clear as mud?

 

[BlaineBug]

It's very different, the AWD transfer case is like having a 3rd center section to prevent wheel hop.

When in Auto the front axle and driveshaft are engaged and turning but the computer is waiting to decide how much power to transfer from the back to the front.

My wife has a Nissan Rogue, all wheel drive. There's a button to "lock" it temporarily. So I would assume that it's somehow clutch based as well as it has both functionalities but is extremely dumbed down in operation for the user.

 

[BlaineBug]

This seems to be somewhat correct, although at what point does the front diff actuator couple the front propshaft (and transfer case) to the diff? It wouldn't be needed if they're already coupled. They are separate until the front diff actuator is commanded on.

At least that's the way mine is on my NP246 AUTO system -- I can tell when the front engages, maybe 1/2 second or so after sensing rear wheel slip. The T/C always keeps the front propshaft spinning at an appropriate speed so the engagement can be quick, but it's not coupled to the diff until the actuator, well, actuates it.

Obviously your newer systems might operate differently, but if there's a front diff actuator, I don't see how. Enlighten me, please.

Running in AUTO theoretically won't cause any additional wear on the diff, unless it's engaged by the computer. Clear as mud?

Our trucks do not have vacuum or electronic actuated hubs like some trucks have. They are always locked full time with the front differential. The transfer case is what is uncoupling the front differential from the drivetrain alone.

I can tell my Auto transfer case runs like having AWD in the sense that it gives power to both front and rear differentials full-time but allows for slippage between the front and rear so that there isn't binding on dry pavement.

 

[Caddylack]

The G80 is not "weak" and does not "break easily."

If you do stupid stuff - burnouts, donuts, etc - yes, it's more likely to break. If you drive with some modicum of maturity, it will outlast you. I have 3 G80 trucks with over 650,000 total miles and have had zero G80 issues.

Everything lasts when you baby it. It's the stupid stuff that I care about.

My dad put 400k miles on a 4L60E, but that doesn't mean anything for me.

 

[swathdiver]

This seems to be somewhat correct, although at what point does the front diff actuator couple the front propshaft (and transfer case) to the diff? It wouldn't be needed if they're already coupled. They are separate until the front diff actuator is commanded on.

At least that's the way mine is on my NP246 AUTO system -- I can tell when the front engages, maybe 1/2 second or so after sensing rear wheel slip. The T/C always keeps the front propshaft spinning at an appropriate speed so the engagement can be quick, but it's not coupled to the diff until the actuator, well, actuates it.

Obviously your newer systems might operate differently, but if there's a front diff actuator, I don't see how. Enlighten me, please.

Running in AUTO theoretically won't cause any additional wear on the diff, unless it's engaged by the computer. Clear as mud?

I've not been very good at articulating how it functions, mostly because I wasn't entirely correct until made so recently on another forum!

Operation in Auto is best explained here:

Gears Magazine - Magna's MP 3010 Transfer Case

The Magna Powertrain model 3010 (MP 3010) transfer case (figure 1) has been the heart of GM’s four-wheel drive truck line since it was introduced in 2011 to replace the New Venture Gear transfer case system. The MP 3010 transfer case is an electronically controlled, one-speed automatic, active...

gearsmagazine.com

The MP3010 is the single speed version of the MP3023/MP3024 and for our discussion works the same.

 

[intheburbs]

Everything lasts when you baby it. It's the stupid stuff that I care about.

My dad put 400k miles on a 4L60E, but that doesn't mean anything for me.

Thanks for the laugh. I've been called a lot of things, but I've never been accused of babying my trucks. They're tools (and toys). My 2001 has been so heavily abused it's wearing rear axle number 4. Not failures of the G80, but from towing heavy. And, BTW, it has the original 4L65 and 325k miles on it.

And I do much worse to the 2500. That's the main reason I bought it. If it's not towing my 8600-lb trailer, it's towing my 4000-lb cargo trailer. And when not towing, it's cruising at 90-100, with brief stints to 110-115.

 

[j91z28d1]

Thanks for the laugh. I've been called a lot of things, but I've never been accused of babying my trucks. They're tools (and toys). My 2001 has been so heavily abused it's wearing rear axle number 4. Not failures of the G80, but from towing heavy. And, BTW, it has the original 4L65 and 325k miles on it.

And I do much worse to the 2500. That's the main reason I bought it. If it's not towing my 8600-lb trailer, it's towing my 4000-lb cargo trailer. And when not towing, it's cruising at 90-100, with brief stints to 110-115.

to be fair none of that uses the locking part of the diff. that's mostly ******* bearings and keeping the fluid cool under load. an open diff would be fine in all that. the rear end itself isn't what makes is considered weak, it's the locking mechanism. if it gets used, it seems is much more likely to break than the standard type of limited slip even gm uses in cars.

 

[VR4Play]

This seems to be somewhat correct, although at what point does the front diff actuator couple the front propshaft (and transfer case) to the diff? It wouldn't be needed if they're already coupled. They are separate until the front diff actuator is commanded on.

At least that's the way mine is on my NP246 AUTO system -- I can tell when the front engages, maybe 1/2 second or so after sensing rear wheel slip. The T/C always keeps the front propshaft spinning at an appropriate speed so the engagement can be quick, but it's not coupled to the diff until the actuator, well, actuates it.

Obviously your newer systems might operate differently, but if there's a front diff actuator, I don't see how. Enlighten me, please.

Running in AUTO theoretically won't cause any additional wear on the diff, unless it's engaged by the computer. Clear as mud?

NP246 auto system works by engaging the front diff actuator full time and applying the clutches in the TC to engage the front axle. There is always a bit of drag on the clutches as they don't disengage completely. Even in 2wd the front driveshaft spins. When the front diff is locked the clutches slip when turning which is what causes the wear. The newer trucks unlock the clutches all the way allowing the front driveshaft to free wheel. The older trucks do not. I don't remember the year break but my 2002 always slight pressure on the clutches and it is difficult to spin the front driveshaft by hand when parked and in 2wd which is why there is a sticker under the hood saying not to run on a 2wd dyno.

 

[j91z28d1]

I've not been very good at articulating how it functions, mostly because I wasn't entirely correct until made so recently on another forum!

Operation in Auto is best explained here:

Gears Magazine - Magna's MP 3010 Transfer Case

The Magna Powertrain model 3010 (MP 3010) transfer case (figure 1) has been the heart of GM’s four-wheel drive truck line since it was introduced in 2011 to replace the New Venture Gear transfer case system. The MP 3010 transfer case is an electronically controlled, one-speed automatic, active...

gearsmagazine.com

The MP3010 is the single speed version of the MP3023/MP3024 and for our discussion works the same.

interesting. mine has a 4low as well. and the manual says it can be shifted into a tow behind a rv mode, basically a neutral. I will have to look into which number I have. like you say, probably works the same way. just 2 gear ratios for low and high,

 

[Z15]

¨ Optional Equipment (G80 Order Code) on all GM two-wheel and four-wheel drive light trucks and sport utilities.

Benefits

¨ Improved traction differentiates the vehicle relative to other rear wheel and four-wheel drive vehicles on the market.

¨ Maintenance free; requires no lube additives.

¨ Enhanced towing and off-road performance.

¨ Patented carbon friction disc technology enhances performance and durability while reducing warranty claims.



Principles of Operation

¨ Wheel speed difference (left to right) in excess of 100 RPM will cause a flyweight mechanism to open and catch a latching bracket.

¨ The stopped flyweight will trigger a self-energizing clutch system, which results in the cam plate ramping against a side gear.

¨ Ramping increases until both axles turn at the same speed (full lock), which prevents further wheel slip.

¨ At speeds above 20MPH, the latching bracket swings away from the governor and prevents lockup from occurring.



Technical Specifications

¨ Automatic locking takes place within a fraction of a second, so smoothly that it is unnoticed by the average driver.

¨ Unlocking occurs automatically, once the need for improved traction is gone, and is unnoticeable to the average driver.

¨ Compatible with anti-lock brake systems.

 

[Z15]

The G80 locker responds to slippage. They do not prevent slippage as a true limited-slip, or "posi" does. One wheel has to get spinning for it to engage. One the right and left RPM and been brought to equal speeds by the clutches, it disengages. Keep in mind that the G80 is mechanically prevented from locking at speeds over 20 mph depending on what size tires you have. Above that speed it behaves just like an open differential. Just like an open differential it is possible to get both wheels spinning under certain conditions without the G80 locking.

These things ARE NOT "performance" differentials. They are intended to be multi-purpose best suited for the average truck/SUV driver in the most diverse situations.

------------------------------------------------------

The “G-80” meaning by GM DOES NOT directly apply to only one differential. That “G-80” moniker is the GM RPO (regular production option) order code for a traction control device in a differential. It has been applied to many different types of traction control systems in both cars and trucks over many, many years (50+). The truck (and SUV) G-80 is a “locker” made by Eaton in 1500/2500/3500 vehicles. The half-ton 1500 units get a lighter duty version for the smaller size differential housing.

 

[BlaineBug]

interesting. mine has a 4low as well. and the manual says it can be shifted into a tow behind a rv mode, basically a neutral. I will have to look into which number I have. like you say, probably works the same way. just 2 gear ratios for low and high,

If you have the 2-speed transfer case, you twist the dial as far as it will turn clockwise until the N indicator illuminates on the knob. The single speed transfer case can also be twisted further to the right as well but there is no neutral and no light to illuminate. I assume the transfer case oil pump is run via the transfer case output shaft rather than pump driven from the transmission output (which wouldn't be turning if you were in neutral.)

I also believe it's destructive to transmissions to flat-tow them if the transmission output is turning but the motor is not running, they'll burn up as transmission pump is run off of the engine crank.

 

[EducatorDan]

Can you clarify this statement?

Obviously G80 doesn't refer to any specific part. That's just the RPO that tells you the vehicle doesn't have an open diff.

You're saying GM has been using that same diff for decades? In what?

Just for reference, the 1996 Impala SS had an Auburn "G80" that was crap. That's an 8.5" 10-bolt.

Sorry what I meant was that i think that ALL RWD or 4x4 vehicles ought to have a limited slip of some kind. Truthfully I'm mildly disappointed in GM that when it comes to trucks or BOF SUVs that any customer has to worry about picking the correct option packages to get a limited slip.

Didn't know the car one was different. The truck one has been pretty highly regarded.

 

[EducatorDan]

The G80 is not "weak" and does not "break easily."

If you do stupid stuff - burnouts, donuts, etc - yes, it's more likely to break. If you drive with some modicum of maturity, it will outlast you. I have 3 G80 trucks with over 650,000 total miles and have had zero G80 issues.

Bingo. I can see how the guys who want to 500 hp or 600+ lb ft through the sucker are going to destroy it. But the average consumer (even those who do tow up to the limits of the vehicle etc.) are likely going to think that the G80 is indestructible.

Most of the truck guys and GM faithful like it because it is a simple mechanical unit and just WORKS.

 

[j91z28d1]

If you have the 2-speed transfer case, you twist the dial as far as it will turn clockwise until the N indicator illuminates on the knob. The single speed transfer case can also be twisted further to the right as well but there is no neutral and no light to illuminate. I assume the transfer case oil pump is run via the transfer case output shaft rather than pump driven from the transmission output (which wouldn't be turning if you were in neutral.)

I also believe it's destructive to transmissions to flat-tow them if the transmission output is turning but the motor is not running, they'll burn up as transmission pump is run off of the engine crank.

yes, I have to turn it all the way to the right and N lights up. it also warns that park will not hold the truck when the transfer case is in N. so maybe the tranny out put shaft is not spinning? so no damage in the tranny side, but would be interesting if the transfer case is being oiled while being towed. maybe the clutche pump isn't running, but maybe something else is spinning enough to splash oil everything?


either way I have no plan to use it. just talking.

I remember the old manaual trannys you don't tow long distance in neutral without the engine running. no pump but same idea, without the input shaft spinning there's not oil being thrown up to the bearings from the counter shaft.

 

[BlaineBug]

yes, I have to turn it all the way to the right and N lights up. it also warns that park will not hold the truck when the transfer case is in N. so maybe the tranny out put shaft is not spinning? so no damage in the tranny side, but would be interesting if the transfer case is being oiled while being towed. maybe the clutche pump isn't running, but maybe something else is spinning enough to splash oil everything?


either way I have no plan to use it. just talking.

I remember the old manaual trannys you don't tow long distance in neutral without the engine running. no pump but same idea, without the input shaft spinning there's not oil being thrown up to the bearings from the counter shaft.

If transfer case in neutral then it is disconnected from the transmission output.

 

[BlaineBug]

The G80 locker responds to slippage. They do not prevent slippage as a true limited-slip, or "posi" does. One wheel has to get spinning for it to engage. One the right and left RPM and been brought to equal speeds by the clutches, it disengages. Keep in mind that the G80 is mechanically prevented from locking at speeds over 20 mph depending on what size tires you have. Above that speed it behaves just like an open differential. Just like an open differential it is possible to get both wheels spinning under certain conditions without the G80 locking.

These things ARE NOT "performance" differentials. They are intended to be multi-purpose best suited for the average truck/SUV driver in the most diverse situations.

------------------------------------------------------

The “G-80” meaning by GM DOES NOT directly apply to only one differential. That “G-80” moniker is the GM RPO (regular production option) order code for a traction control device in a differential. It has been applied to many different types of traction control systems in both cars and trucks over many, many years (50+). The truck (and SUV) G-80 is a “locker” made by Eaton in 1500/2500/3500 vehicles. The half-ton 1500 units get a lighter duty version for the smaller size differential housing.

I tend to feel as though this G80 limited slip bites harder as I will get binding on dry pavement until it automatically unlocks. With my Ford 8.8 limited slip "Trac-Lok" even after I rebuilt it with brand new clutches, shims, Z spring, and fresh gear oil + additive I never recall it actively binding on dry pavement at low speed. And that was with car tires too, smaller diameter.

 

[Geotrash]

I tend to feel as though this G80 limited slip bites harder as I will get binding on dry pavement until it automatically unlocks. With my Ford 8.8 limited slip "Trac-Lok" even after I rebuilt it with brand new clutches, shims, Z spring, and fresh gear oil + additive I never recall it actively binding on dry pavement at low speed. And that was with car tires too, smaller diameter.

I've never experienced binding like that in any of my G80-equipped trucks over the years. I suspect an issue there.