Home Forums Gear Hunting Trucks and Four-Wheel Drives Eaton G80 locking diff.

Toad is correct. The G80 is the designation by GM, but all G80's are made by Eaton. Different sizes of the same locker for different size vehicles. The ones with the worst rep are the 1970s models they put in the 14 bolt due to them grenading when they spool up one tire spinning and then lock up.

But not all G80's are the same differential. And there're others besides your dreaded gov-lok.
Someone posts he bought a truck with G80 option. Didn't say what truck it was but right away you start blasting.

The G80 just means limited slip.......different rearends according to which vehicle it goes into. There are several versions of the G80 option......the 14 bolt diff is a real good one.

See, that's where you are wrong...ALL the G80's in TRUCKS are the Eaton M Locker, also known as the Gov Lock. The G80 option in CARS is a different limited slip or posi unit, but he TRUCKS(all models) are the Eaton locker, just different model numbers depending on which axle the truck has.

See below:
Here's the service bulletin from GM about the proper lubricant and use of additives (I added the bold and underline):

GM Said:

LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION) #91-4-109
SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT - (SERVICE INFORMATION)
VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS
Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.
This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.
To correct this condition, drain and refill the rear axle with SAE 80W-90 GL5 (P/N 10950849).

The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.

VEHICLES/COMPONENTS INVOLVED: ------------------------- ---- Some light duty trucks equipped with locking rear axles, RPO G80.
SERVICE PARTS INFORMATION:
Part Number Description ----------- ------------------ 10950849 Lubricant, Rear Axle (1 litre)
Parts are currently available through CANSPO.
WARRANTY INFORMATION:
As specified in Light Duty Truck Maintenance Schedules, locking rear axle fluid drain and refill is required owner maintenance at the first engine oil change. Failure to drain and refill the rear axle as specified may contribute to a later axle chatter condition. Refer to the appropriate Light Duty Truck Maintenance Schedule or service manual, section OB, for further details on change intervals.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
� Copyright General Motors Corporation. All Rights Reserved.


I'm not sure how much more clear I can be. The OP said he bought a TRUCK with the G80 option, therefore he has an Eaton M Locker or Gov Lock...

Jamison....none of this service bulletin crap has anything to do with anything. If you're saying that all GM limited slips are gov loks, and all gov loks break, you're simply full of sh#t.

Jamison's original BS. No clue which truck Elk has, or which rear end his G80 refers to. Is it an 11.5", 10.5"? Or a smaller 10 bolt? The 14 bolt is a G80 code. And one of the really strong differentials out there. Handles unGodly abuse. Most DMax diesels come with the towing options and is equipped with the G80 limited slip option, I haven't seen a sticker without them. No the G80 doesn't break when you pull something or run an oversized tire. And it's not the same differential as in my '94 light duty 3/4T. Or small block gas trucks. Go to a GM diesel forum....a great many of those guys have modified engines, some extremely modified. A great many of them race. Lots of them tow heavy. And most run oversize tires. Ask now many differentials have broken.

Trying to come on like the authority. Now you're waffling. You and that toad guy....a couple of toads.

you are still 'confused' (at best). IF his truck has the G80 option, it WILL have the Eaton Mlocker 'Gov lock'.

Wow. That took all of 30 seconds to find.


Duramax forum. 2008 black LMM CC/SB 4x4
"So i was going to change the fluid in my Duramax with the G80 locker and found a piece broken inside. My truck is pretty much stock."
Duramax diesels forum. 07 2500HD CC LBZ
"G80 sucks. This has to be the most disappointing part of this truck."
"IMHO the g80 sucks i have broke 3 of them and it cost alot of money each time."
diesel place forum. "DMAX 2500HD. My truck is sitting at the dealership right now getting the G80 differential torn down due to excessive metal shavings after only 5000 miles."
06 Chevy CC/SB 4x4
"My g80 just snapped some ring (3 places) on the drivers side of the diff."

I'm trying to figure out where I am waffling. I showed you a GM Service bulletin where it plainly states that the G80 option in TRUCKS are LOCKERS, not limited slips. There are many places online, including your beloved diesel forums, where you can plainly find info that ALL G80 LOCKERS in TRUCKS are the Eaton MLocker. It doesent matter which truck or rear end the OP has, if it is in a truck, it is an Eaton M Locker or GovLock. Just different versions of the same design....

You are making yourself look like a retarted kid who can't read and comprehend what is plainly put before you, so you have to resort to referring everyone to other forums where I have already been and found that majority of people there only run them until they can afford a real locker...See the post above.
I am going to agree to disagree on this subject and leave it alone. I like to read the forums for enjoyment, and not once did I ever claim to be an expert othis subject,, I merely passed along first hand info from the rigs I have seen in my Offroad club. You feel free to rant and rave all you want now, you are the one making yourself look like a fool.

Bull Elk mentions G80 option on his truck, doesn't say anything about which truck. And you come on with this bullsh#t. G80 is the GM designation for limited slip or traction control or whatever you care to call it. In anything from Camaro or Caprice to S-10's to 1 ton HD pickups. Neither GM nor Eaton have ever called anything "gov-lok", even the particular trouble prone unit you're talking about. Along with Auburn, Eaton makes lots of different units and one is a really good limited slip differential. The G80 option 14 bolt is very strong.

1) The G80 option not strong enough to tow? Are you friggin' crazy? Again, complete nonsense. The GM diesel trucks are madefor towing, the G80 option is basically standard on them. They're very strong. Hammer these things on the dragstrip with slicks, they don't break. Guys sledpull with them. And I couldn't even tell about all the people - just the ones I know personally - who regularly work the crap out of their trucks towing way over GM max spec.

2) The G80 won't hold up to oversize tires? That's a real dumb one. Just as many GM diesels out there with oversize tires as not. And lots of tow rigs have oversize tires.

You should just keep quiet about this stuff. It doesn't make you look like an authority, makes you look like a dope.

read slowly so you can maybe understand. if it is a GM Truck and has the G80 option, it WILL have the Eaton Mlocker (commonly called the 'Gov Lok') installed when shipped from the factory.

Like I said, obviously you can't read or comprehend facts so I am going to agree to disagree and move on...

After reading this thread I have determined that a G80 differential is ...


THE BEST IN THE WORLD !!!

LOL

Jamison you're absolutely right. The G80 is that eaton nonslip. You'd been going on about how bad they are, but since the 11.5" unit holds up really well I thought it must be some other Eaton, maybe a true track. But they're all that same basic Eaton unit in 4 or 5 different sizes for different sized gears.

Like shooting forums, lots of people go onto several of the different diesel forums. Diesel forum guys are into modifications and performance and very often push the limits. And like with other forums, when something breaks or doesn't work right it's often because that thing is a pos. And they tell everyone. There's hardly ever "the rest of the story".......how much hp, no traction bars(?), what caused/preceded the failure - huge abuse, maybe they'd been fooling with it, wrong lube, no lube, what previous owner did? or who knows what. The Dmax forum you mention has 527 members and several postings about G80 failures. And whenever you see a posting like that on any forum there're also a whole bunch more people talking about no problems and how much they like it. You probably didn't see those.....or the guy who said he was wanting a G80 for his Dodge "because the Torsen unit keeps crapping out."

I'm surprised there aren't a whole lot more with problems. Consider there are more than 1.5Million G80's out there behind Dmax's alone. Add non-diesel trucks and SUV's and all the other applications over the last few decades and that's a huge number of G80's. Majority of truck and suv owners don't go on forums and they leave things stock. They just buy 'em and use 'em. Like a friend in Texas....been using DMax's since '01 for towing a cattle trailer - 19,000 lbs loaded - about 50k miles/yr all over Texas in a lot of 100+ degree weather. No broken differentials. Here in mountain snow country my dealer sells very few cars, mostly trucks and suv's. Each is G80 equipped. The service dept fixes "maybe" one per year. The parts manager said about 10 to the service dept in his 15yrs there. Very few problems.

If mine ever goes it won't be because it's crap. It'll be because I've enjoyed running it for years with 3-4X factory power at the wheels.

Believe it or not, I own one, too. Had one in the truck before my wife's current Suburban. Had one in the Suburban before that... None of them completely crapped out yet, so I am not an internet commando talking about something I don't own. Had one issue with the first Suburban, it would lock up in a turn occasionally and sound like it was coming apart at the seams...
I know there are LOTS of them out there, and like the Walker trigger in a Remington 700, not all of them are bad. BUT, just like the Walker trigger, there is a basic flaw in the design. There has to be a 100 rpm difference in the two wheels before it locks.
When you spool up a 38"+ tire in the air or dirt and then catch it on a rock or hard ground, the casing of the locker is weak enough that that centrifugal force CAN cause it to grenade. They are amazingly sturdy when you are on flat ground (asphalt) on a track or street and both wheels have a good bit of traction, whether racing or towing, and you don't violently start or stop one tire while the other one is moving fast.
Its a well known fact that the guys like me on the rocks will find a weak point if there is one. That is why I directed the OP to a real offroad site like Pirate4x4 to do some research. His only question was about the positives and negatives-- You gave him the positives, I gave some negatives. Neither of us know what his intended use for the truck is, so he will have to decipher the facts and decide for himself...

There are over 1.5 million Duramax equipped vehicles out there, but just because they have DMax, doesn't mean they have a G80 differential. Like most things, they are an option.
Point taken though on the sheer number of them out there across several vehicles lines.

I'm an "expert" on G80s so just to clear up some common misperceptions about recommended gear oil here's the skinny.

The Bulletin that Jamison posted is one source of confusion and in particular this part ...

The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.

From the above it seems as though friction modifiers are not recommended for use in G80s but that's not quite right.

Automatic Locking Differential Lubricants. [Note from Michael Asmussen, Torque Control Products Division of Eaton Corp.] We recommend the following lubrications for our locking differentials:
1)Texaco 2276; Synthetic 75 W90; Gm Part # 9986115
2)Texaco 9622; Mineral based 80W90; GM Part # 9985290
3)Texaco 2080; Synthetic 75W140 (heavy duty applications); GM part # 9985991
Note - All of the above lubes are preblended with friction modifier. No additional modifiers are necessary or recommended. As far as other lubes are concerned, any standard GL 5 lube will work, but the units perform optimally with the three listed above.

All common gear oils have FMs which is acceptable provided they don't contain a high concentration and they do vary. I called Valvoline and their Performance dino gear oil contains 3% FM. Other brands can have as high as 8% FM.

Here's another issue concerning the use of synthetic gear oil from Amsoil.

[5] Do not use synthetic lubricant in axles using RTV sealant.
American Axle has only approved the use of Synthetic GM P/N
12378261 as follows: All 8.6" rear axles.All 9.5" rear axles
built before mid-FEB 1998 are not compatible, after mid-FEB
1998 are compatible.All 10.5 inch rear axles built prior to
March 3, 1999 are compatible if axle shaft hub RTV sealer
is replaced with GM gasket P/N 327739.

Hope this helps anyone that wants to service their dif.

The G80 is standard on Dmax trucks. If you buy a Dmax,you get a G80 in the diff.

It hasn't always been the case and not every Dmax goes into an noncommercial HD truck.