Eation G80

3500duramax · December 1, 2003

I just found out the other day while i was replacing the axle seals that i have the G80 eatin unit in my rear end. Is this a locker or posi, limited slip? what is it and is it reliable. also would any of you guys have a list of what the codes in my glovebox mean in my 1995 silverado?? Thanks

Ben · December 1, 2003

Eaton page explaining it's a locker and LS

Do search of this site on "RPO". There will be listings and hot links to sites that have RPO codes listed. If you can't find, repost and I'll post hot links.

Mega Dogmeat · December 1, 2003

It's a part time mechanical locker. It's not a limited slip or a full-time locker, like everyone seems to wanna call it.

While it isn't as nice as a full-time locker, it is most definatley better than an open diff or posi

ok I take that back, it says there it acts as a limited slip, but I really don't see how? limited-slip is the same thing as posi, right?

Redapple · December 1, 2003

There is a differnece between Posi & Limited Slip

Basically, the difference between the two is this: A limited slip differential sends power to the non-drive wheel based on input torque; that is, power coming to the axle from the engine.

So, when high torque comes to the differential and both wheels are on a high traction surface, like a drag strip or country road, and high torque is delivered to the axle, the clutch pack clamps the gears to the differential case. This clamping action is in proportion to the torque delivered. The higher the torque, the higher the clamping load.

The idea here is to prevent wheel slip -- at either wheel -- in the first place. If one wheel starts slipping before the other, the clamping force drops in proportion to the torque delivered to the slipping wheel.

The whole point of the torque sensing limited slip differential is to reduce the likelihood of wheel slip.

The locking rear differential locks the drive and non-drive wheels together based on wheel slip at the drive wheel, regardless of engine power input.

Bill

JayMan · December 1, 2003

Well, the G80 is both a locker AND a limited slip.

There is a clutch pack inside the housing with Carbon Fiber clutch plates. That part is exactly the same as a Limited Slip. The difference is in how the plates force together.

With a Limited Slip, there is a preload spring between the Left and Right plates, with a preload spring that always presses against them. As mentioned in the posts, this reacts to input torque, not to wheel speed difference. You can make the clutch pack engage earlier and stronger by using a stronger preload spring, but this increases friction/wear and noise (Chatter).

You can see that the regular Limited Slip is all but useless for offroad. Unless you really floor it, you can only transfer about 10-30% of the torque to the other wheel that's sitting high and dry. If you have a hot rod and do a nice smoky burnout, it seems to work nice!

A true locker is all mechanical: Detroit Locker, PowerTrax Lockright and NoSlip, and Torsen. The Detroit Locker and Lockright are engaged all the time but disengage (Overrun) when one wheel goes faster than the other, like around a corner. That overrun action makes noise: CLANK CLANK CLANK or CLICK CLICK CLICK.

The G80 uses a flyweight governor that senses the difference in wheel speed at SLOW speed. Beyond a certain speed difference, it latches and forces a pawl to push the clutch plates together. When not needed, there is much less friction and wear.

Eaton has a nice URL with lot's of examples on how the thing works:

http://www.traction.eaton.com

Lou'sZ · December 1, 2003

O.K., related question. I have this axle option in my 98 Z71. Do I have to use the 4 oz. of friction modifier when using mineral oil(not synthetic). Is the dealer the only place to buy the friction modifier. I don't want to use synthetic, not sold on it.

robsawatsky · December 1, 2003

I believe synthetic gear oil is the only thing recommended for GM rear axles. If you use the GM specified fluid, it doesn't need any additional friction modifier.

Butch 02 Denali · December 1, 2003

You can get the additive at any automotive store. I highly recommend synthetic, It has proven itself to be better, but if you do use non-synthetic add the friction modifier.

Butch 02 Sierra Denali

JayMan · December 2, 2003

Lou'sZ: I see that you've discovered the contradictory advice given by GM and the "official" Eaton FAQ!

"Eaton strongly recommends utilizing an API-GL5 approved Mineral-Based 80W-90 Axle Lubricant and one 4-oz bottle of Limited Slip Additive (GM or Ford). "

Since the regular Eaton LS and the factory G80 "locker" both use the same Carbon Fiber clutch pack, you wonder who to believe, don't you??

You have to be VERY careful using a synthetic gear oil in any LS differential. Most synthetic gear oils are so slippery, the clutches will slip and chatter. When Eaton claims their LS / G80 doesn't need any additives, they ASSUME you're using the correct gear oil!

Most regular GL-5 80W-90 gear oil will claim "suitable for limited slip applications," which means the additives are already blended in. If you have pails of commercial synthetic gear oil sitting around, like I do, be careful. The commercial stuff that meets Dana extended warranty service is unsuitable for the G80 or a LS: the clutches will slip and chatter.

Yeah, Been There Done That I got mixed up on my 2000 GMC and accidently put in the commercial stuff. Three months later, the first snowstorm and the G80 was slipping and chattering like crazy. I drained out the commercial gear oil and added 2 tubes of friction modifier to Mobil 1 Gear Oil. That seemed to "cure" it!

The really expensive Delco / Goodwrench synthetic gear oil ($24/ gt) has the additive blended in. So does Mobil 1 Gear Oil 75W-90 ($5.25 / qt). The Amsoil gear oil also claims to have the additive blended in (Amsoil dealer help me out here!). If in doubt, squirt in a tube of additive.

I've had good luck with the CRC / Trans-X Posi-Trac additive, which is a 7 fl oz tube. It claims to meet GM, Ford, and Chrysler LS specs: "Prevents chattering, jerking, and slipping ... mixes with any gear oil." This stuff really helps if your G80 is starting to act up. I paid $7.20 at NAPA this summer.

5.3LSilverado01 · December 3, 2003

I recenlt changed my rear axle fluid, some of the scenceing gear teeth on my G80 are stripped. It seems like every 7th one is gone, and theres a patch of like 8 gone.

Lou'sZ · December 3, 2003

Hey JayMan, so if the lube container says suitable for LS differential-do I or don't I add the friction modifier in the mineral based oil? Seems like if I don't have to, then I should look for one that says "suitable...". Easier with less cost. I previously had a T100, that I had a Lock-Right installed in the rear axle. The installer filled the diff. with synthetic fluid. The first thing I noticed was, that I could hear a low roar from the rear axle while driving. A couple of days later, I drained the synthetic and replaced it with mineral-based oil. No noise, completely quiet! In my opinion, synthetics may give longer service intervals but don't have better lubricating qualities. Just my opinion-don't kill me.

JayMan · December 4, 2003

I recenlt changed my rear axle fluid, some of the scenceing gear teeth on my G80 are stripped. It seems like every 7th one is gone, and theres a patch of like 8 gone.

oh no ....

Please tell me your truck is still under warranty?? YEESH!! How many miles on it when you noticed this?

Lou'sZ: That's a great question, and I've never killed anybody yet for their opinion

The Eaton FAQ is pretty clear in that they want you to use the 80W-90 AND the LS additive. It seems they need more LS additive, but that's true of almost all LS designs.

It won't hurt to use more additive, and if you have a "problem" G80 or LS, 2-3 tubes of additive may be necessary. I wouldn't use more than 4 tubes as you might have reduced gear life. But if the thing is already that messed up ...

The LockRight is a mechanical design locker that, like the Detroit Locker, stays engaged ALL the time, until you turn a corner at slow speed. Did your's go CLICK CLICK CLICK around a sharp corner?

How many miles did your T100 have on it when the LockRight was installed? In a previous post I copied part of the Eaton Dana TSB for their HP-40 single reduction tandem truck axle with Spicer LMS hubs. Dana does NOT want you to switch to a synthetic gear oil if the unit has more than 5,000 miles on regular gear oil. Too much can go wrong.

The mineral based 80W-90 probably cushioned your T100 Toyota axle better. The synthetic is much more slippery and thinner, so if there is already wear, you will get noise. I'd say if the axle was run on mineral gear oil, don't change it to synthetic. If it's new, break it in for 600 miles, then change to synthetic.

5.3LSilverado01 · December 4, 2003

52K miles, so no warranty. The locker still works (can lay down 2 equal black marks). But it feels weak sometimes like when 1 tire in dirt and 1 tire on cement. Before the cement tire would spin with the dirt tire, but now, it will barley sqeel (not like i do that all the time, just a few, 3-4, times). Or when giving power on a corner..... If not enough throtle is given to swing the back end around, 1 wheel will spin a little faster than the other...

chris.

Lou'sZ · December 4, 2003

JayMan- yes the Lock-Right went click..click.. around corners. It also caused low speed surging when turning tight, like into a parking space. As you probably know, both of these are normal with the Lock-Right. At the same time, I had 4.56:1 gears installed as well as new bearings(truck was 2x4). My concern with synthetic is that people report that mechanical components leak after switching to the synthetic. If it's thin enough to leak out, how can it cling to mechanical parts and provide protection?

JayMan · December 4, 2003

52K miles, so no warranty. The locker still works (can lay down 2 equal black marks). But it feels weak sometimes like when 1 tire in dirt and 1 tire on cement. Before the cement tire would spin with the dirt tire, but now, it will barley sqeel (not like i do that all the time, just a few, 3-4, times). Or when giving power on a corner..... If not enough throtle is given to swing the back end around, 1 wheel will spin a little faster than the other...

chris.

Chris, your options are very limited unless you're willing to do or pay for a rebuild. How often did you change your rear gear oil?? If you get the detailed gear advice from places like Randy's Ring and Pinion, they're adament on how you treat the axle during it's first 600 miles of life.

Eg: no trailer towing or heavy loads at all, moderate speeds (Preferably city/town driving), no extended high speed Interstate driving, etc. Then after 600 miles you change the gear oil, use a synthetic or a good quality mineral oil, and change it every year or 20,000 miles. They also recommend another gear oil change within 600 miles of towing for the first time.

When you had the rear cover off, was there a lot of filings on the magnets? Where these filings powdery (Normal wear particles) or were they actual chunks of metal (NOT normal)? Any sludge or thick residue on the case or cover?

With the axle cover off did you inspect the ring gear for scoring, nicks, heat cracking, and other abnormal wear? With the rear axle safely supported on jack stands and the trans in neutral, have somebody turn the rear wheel or driveshaft. This is the only way to inspect all of the ring gear teeth. Randy's Ring and Pinion has links for maintenance and they have pictures of normal and abnormal wear patterns. So does the Helm shop manual.

All I can suggest is draining the axle, putting in two tubes of CRC / Trans-X Posi-Trac additive (Total 14 fl oz, see if NAPA or Autozone carries it), and the approved rear axle fluid, like a mineral based 80W-90 or Mobil 1 Gear Oil. Drive around and see if your GovLok comes back to life. If not,

Sorry.