Locking Differential G80 code

[ManyCamaroz]

Wasn't sure where to post this thread. I figured the Engine/Transmission and Rearend was part of the drivetrain so here it goes!

 

I have a '99 Yukon OBS that has RPO Code G80 (locking differential) and GT4 (373:1 ratio) on the rpo code list in the dash box.

 

I know that with yesterday's posi-traction that if you rotated the wheel on one side the other wheel would roate in the same direction and the standard rearend would rotate in the opposite direction.

 

Question: Does a locking differential act the same way as a posi-traction? I rotated my wheel and the wheel on the other side rotated in the opposite direction.

 

If I remember correctly the locking differential does not have friction plates, thus not requiring the posi-traction additive (friction modifier). I had a '92 Yukon that had a locking differential and it did not require the posi-tracion additive because of metal to metal engagement instead of friction plates. Is this correct?

[MS3DALE]

Your rear end is fine,it is normal for the other wheel to rotate in the opposite direction with the locking-diff. and when on the road it will only lock at speeds up to 20 mph. and no you do not use friction modifier in the GM-Eaton locking diffs.

(All my 8 trucks I have owned over the past 16 years had the G80 locker and that is the way they worked)

[ManyCamaroz]

MS3Dale

 

I assume that your username is referring to 'Miss # 3 Dale Earnhardt", is this correct?

 

That's interesting if it is, because I live where the majority of the Nextel Cup Drivers reside. I live about 3-4 miles from Dale jr. now. Before Dale Sr. built his log cabin (mansion) over by his new race shop in the late 90's he lived across the cove from me, where Dale Jr. grew up. It was nothing special just a nice older average home in a quiet town on Lake Norman. We lived in the Dooley township of Mooresville (aka: Race City USA), N.C. . It is no longer the quiet town it once was since most of the race shops are here and the crew members live in the area.

[MS3DALE]

Man, what a good guess,your right on the user name, and guess what? I'm down your way all the time for the races,I was just down there this past weekend for a car show at DEI,my buddy works at Dale Earnhardt Chevrolet and he lives in Newton, I know right where Dooley is,Do you still live there?I go through it all the time on Hwy.150 on my way to DEI. And your right,its no longer a quiet town,they keep building and building!!

Talk to you later, Rich.

[ManyCamaroz]

I live off of Perth Road. If coming from Newton into Mooresville once you pass "Big Daddy's" Perth Rd. is the next light. I live down Perth about 1.3 miles on the left.

[MS3DALE]

Yep,Small world,I know right where your at!! And Big Daddy's has awesome food!!

And by the way did my answer about the locker help you out at all or did I just confuse you?

[ManyCamaroz]

Yes, I understand what you are saying.

 

I'm due to change the gear oil in about 5k miles and wanted to know what to expect. I saw where the manual says to only use GM #blah blah blah. I that it is only 75w 90 synthetic.

[MS3DALE]

No,For a '99 Yukon ("Old-Body-Style") you use GM#89021671 non-synthetic 80W-90 gear lube,although you could use sythentic if you want,I wouldn't though.Just my .02 cents.

[Butch 02 Denali]

Any gear oil 75-90 or 80-90 rated GL5 will be fine for the GM G80. Synthetic is always highly recommended for all uses. The factory recommended oil for G80 has posi additive in it already, and is required for the clutches, it is actually a combination locker/posi unit.

 

Butch 02 Sierra Denali

[malibu795]

2kflhr

 

couple questions...i assuming that the rear axle was cpmplety of the ground. if the trans was in park the tire would rotate in oposite direction. due to the way the diff is designed. with the trans in nuteral the tire will spint the same direction.

 

reaon why they in opostie dircetion when the driveshaft is lock is trans in park..is the diff alow the inside tire to rotate ate a slower speed than the out side tire alowing the vehicle turn trun easier ms3dale is right a normal open diff and the driveshaft locked the tires will spin in oposite direction

 

 

 

wildman

[PeterbiltChrome]

take it apart an learn how it works ~ experiment with it and you'll start to understand. If you've ever parked on a hill with it in park with ice on one side, the driveshaft won't turn, but the wheels will spin opposite of each other. If you drive one side on ice, one wheel will spin out until it reaches a certain rpm difference to that of the other wheel where in turn, the locker will kick in and you will have 2 wheels locked together.

[sirhuntalot1]

take it apart an learn how it works    ~  experiment with it and you'll start to understand.  If you've ever parked on a hill with it in park with ice on one side, the driveshaft won't turn, but the wheels will spin opposite of each other.  If you drive one side on ice, one wheel will spin out until it reaches a certain rpm difference to that of the other wheel where in turn, the locker will kick in and you will have 2 wheels locked together.

 

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I just changed out the diff fluid recently and I put the additive in my g80 4.10's and was told that it did not need the additive so I called the GM dealer and asked the mechanic on duty He said it would be fine with it in there. Anybody ??? It would be my luck that I get a hold of one of the stupid ones that doesnt know his butt from a hole in the ground and mess up my re.

[builderpaul]

take it apart an learn how it works    ~  experiment with it and you'll start to understand.  If you've ever parked on a hill with it in park with ice on one side, the driveshaft won't turn, but the wheels will spin opposite of each other.  If you drive one side on ice, one wheel will spin out until it reaches a certain rpm difference to that of the other wheel where in turn, the locker will kick in and you will have 2 wheels locked together.

 

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I just changed out the diff fluid recently and I put the additive in my g80 4.10's and was told that it did not need the additive so I called the GM dealer and asked the mechanic on duty He said it would be fine with it in there. Anybody ??? It would be my luck that I get a hold of one of the stupid ones that doesnt know his butt from a hole in the ground and mess up my re.

 

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Feel free to correct me if I am wrong but the additive is for limited slip diffs. The limited slip has clutches that need to be able to smoothly slip when turning corners. Trucks don't have limited slip they have lockers (g80) these clutchs are not designed to slip they lock just like your clutch on a standard shift. You will not damage it with the additive but it my not work as disigned. The additvie my cause it to slip instead of lock.

[biochemist]

Hello, you do not need the additive...BP is right, it may make it work incorrectly. I had mine changed recently and asked the tech if the G80 needed the additive, he said the grape juice already has everything you need, no extra lube needed. I think all rated (high-quality GL5) synthetic rear end/gear fluid is acceptable with the G80, this is all you need...search around for a bit you will see other posts on this matter, I posted one below for you . Hope this helps, later,

 

http://www.gm-trucks.com/forums/index.php?...461&hl=additive

[Z man]

Hello all check out this sites from eaton thay are the makers ofGM's

g-80.

http://www.traction.eaton.com/prod2.htm

http://automotive.eaton.com/product/tracti...ockingdiff.html