Offroad Trailblazers and Envoys

Lockers/axels/ratios Point me in the right direction?

G80, GU6, GT4, GT5, WTF? This section is for gearing and driveline stuff.

by Trail X » Thu Jul 14, 2011 2:19 pm

Bill hasn't done a good job of updating this site with some of his old threads on Trailvoy. :poke:
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by Flying Monkey » Thu Jul 14, 2011 2:21 pm

So he was running a 4.10 gear rear but not front?
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by janesy86 » Thu Jul 14, 2011 2:27 pm

No he's running 3.73's IIRC. Got the 8.6" to match his front...
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by Diacom » Thu Jul 14, 2011 2:29 pm

djthumper wrote:
Flying Monkey wrote:my original plan was to start hitting junk yards and such to try to find just a better geared G80. Want at least a 3.73. I think the 3.73 would be better on 33's then my 3.42 (non-G80). And if I go to 35's later with BL ill definatly need something higher then then 3.42.



If you are looking at re-gearing anyhow I would only want to do the front and rear once. I would just get an 8.6 rear end and start setting that up with 4.56 gears. They will give you plenty of torque with the 33's and if you decide to go to the 35's later will still provide you with plenty of torque take a look at this gear ratio guide to see what I am talking about. It isn't that our engines lack power, it actually gives us a slight advantage to make up a slight loss of torque. But we can have all of power in the world and the truck won't move without torque.


This is the way I plan to go. I have the 8.6 open, the Richmond No-Slip and atm 3.73's to match my front end. Hopefully next year with a BL and upgrade in tire size again, I'll do my 4.56 gear swap at that time at both ends.

Flying... was the one you found with the G80 an 8.0 or 8.6 rearend? That's a good price either way, but just hate to think you'd have to purchase another diff later when you want to upgrade.
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by Flying Monkey » Thu Jul 14, 2011 3:42 pm

Diacom wrote:
Flying... was the one you found with the G80 an 8.0 or 8.6 rearend? That's a good price either way, but just hate to think you'd have to purchase another diff later when you want to upgrade.



Not sure how to tell. when i search their part number i dont get any real answers. Looks like i have more research to do, in order to know which is which
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by fishsticks » Thu Jul 14, 2011 8:21 pm

An auto locker is a device like a lunchbox or Detroit Locker, which locks when power is applied. A G80 is NOT an auto-locker. A G80 requires one wheel to slip/spin before it tries to do anything. This is bad for a number of reasons, and unlike any locker out there. GM doesn't even call it a locker. RPO codes list it as "Axle, positraction limited slip" and it's designed for street manners, not abuse. (Citation: http://www.trailvoy.com/docs/vinrpo/2002_VIN_RPO.pdf)

I don't like being a hater but I watched yet another G80 go in a full size on the last trip I was on. He was on a blue trail trying to get over a tree root. Not much wheelspin at all and his ratchet failed. We pulled it out and he ran open the rest of the trip.

Honestly guys, If all you're after is the G80....buy a much easier to find 8" rear end. The G80 WILL fail before the ring and pinion does. I can't think any failure I've seen/read about not being caused by a snapped ratchet, exploded spider gear or broken carrier case. Upgrading to an 8.6 G80 isn't addressing the actual weak point of the assembly.

If you have a G80 already, great. Use it until it dies. But it's a waste of money to go 8.6 with the G80 unless you are set on regearing lower than 4.10... and if you are regearing, you'll have he carrier out anyway, and can install a real locker.

Save up, do it once, do it right.
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by Flying Monkey » Thu Jul 14, 2011 8:51 pm

fishsticks wrote:An auto locker is a device like a lunchbox or Detroit Locker, which locks when power is applied. A G80 is NOT an auto-locker. A G80 requires one wheel to slip/spin before it tries to do anything. This is bad for a number of reasons, and unlike any locker out there. GM doesn't even call it a locker. RPO codes list it as "Axle, positraction limited slip" and it's designed for street manners, not abuse. (Citation: http://www.trailvoy.com/docs/vinrpo/2002_VIN_RPO.pdf)

I don't like being a hater but I watched yet another G80 go in a full size on the last trip I was on. He was on a blue trail trying to get over a tree root. Not much wheelspin at all and his ratchet failed. We pulled it out and he ran open the rest of the trip.

Honestly guys, If all you're after is the G80....buy a much easier to find 8" rear end. The G80 WILL fail before the ring and pinion does. I can't think any failure I've seen/read about not being caused by a snapped ratchet, exploded spider gear or broken carrier case. Upgrading to an 8.6 G80 isn't addressing the actual weak point of the assembly.

If you have a G80 already, great. Use it until it dies. But it's a waste of money to go 8.6 with the G80 unless you are set on regearing lower than 4.10... and if you are regearing, you'll have he carrier out anyway, and can install a real locker.

Save up, do it once, do it right.



Very good write up thank you.
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by MrSmithsTB » Thu Jul 14, 2011 9:09 pm

Donny is wise beyond his ears. I know that swapping axles and installing a locker is something that I will do hopefully before any kind of detonation. Having 3.42 gears, I am still on the fence about changing ratios, as I really don't plan to go any larger than 33" and they didn't seem to slow me down before.
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by fishsticks » Thu Jul 14, 2011 9:13 pm

Flying Monkey wrote:Very good write up thank you.



Here's some anecdotal information on lockers in general, along with a comparison of ARB (selectable) vs Detroit (auto).

http://www.stu-offroad.com/misc/locker-1.htm

TLDR Version:

ARB downsides: Lots of components = lots of points of failure, higher maintenance.

Detroit downsides: Snap an axle shaft and the resulting backlash can/will destroy the Detroit.


Here's a write up on the difference between lunchbox lockers and Detroit full carrier replacement auto lockers.

http://www.offroaders.com/tech/Lunchbox-lockers.htm
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by snowmirage » Thu Jul 14, 2011 10:02 pm

fishsticks wrote:An auto locker is a device like a lunchbox or Detroit Locker, which locks when power is applied. A G80 is NOT an auto-locker. A G80 requires one wheel to slip/spin before it tries to do anything. This is bad for a number of reasons, and unlike any locker out there. GM doesn't even call it a locker. RPO codes list it as "Axle, positraction limited slip" and it's designed for street manners, not abuse. (Citation: http://www.trailvoy.com/docs/vinrpo/2002_VIN_RPO.pdf)

I don't like being a hater but I watched yet another G80 go in a full size on the last trip I was on. He was on a blue trail trying to get over a tree root. Not much wheelspin at all and his ratchet failed. We pulled it out and he ran open the rest of the trip.

Honestly guys, If all you're after is the G80....buy a much easier to find 8" rear end. The G80 WILL fail before the ring and pinion does. I can't think any failure I've seen/read about not being caused by a snapped ratchet, exploded spider gear or broken carrier case. Upgrading to an 8.6 G80 isn't addressing the actual weak point of the assembly.

If you have a G80 already, great. Use it until it dies. But it's a waste of money to go 8.6 with the G80 unless you are set on regearing lower than 4.10... and if you are regearing, you'll have he carrier out anyway, and can install a real locker.

Save up, do it once, do it right.



All valid points and good advice. Myself I am just getting into this, I've wanted to do it for a long time but I'm just getting the ball rolling. I have no intention in the near future of running anything much bigger than my 31" tires. Is the G80 in either axle ideal? Nope but its better for getting myself out of trouble now and then than an open diff. And upgrading to the 8.6 will be at least a bit stronger than the 8" not a lot as you said but some. And it gives me some options to upgrade it later on to something that works better.
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by Trail X » Thu Jul 14, 2011 10:41 pm

fishsticks wrote:An auto locker is a device like a lunchbox or Detroit Locker, which locks when power is applied. A G80 is NOT an auto-locker. A G80 requires one wheel to slip/spin before it tries to do anything. This is bad for a number of reasons, and unlike any locker out there. GM doesn't even call it a locker. RPO codes list it as "Axle, positraction limited slip" and it's designed for street manners, not abuse.


I'm sure the definition varies depending on where it's looked up, but my understanding is all types of torque altering differentials are infact "limited slips". Any that will fully lock the left and right wheels together with no differential in speed no matter the situation is considered a "locker". "Positraction" is just Chevy's trademarked name for a locker.

"Auto locker" means automatic locker, right? As in - no manual intervention required. So I believe the lunchboxes and the G80 are technically in the same category - unless there is something else to the definition that I'm not aware of.

My opinion of getting the 8.6" with the G80 is so you can then save money for a locker but you won't be without a locker during the time you're saving... but that line of thinking goes hand in hand with a non-lunchbox locker.

Semantics really.
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by bartonmd » Fri Jul 15, 2011 8:05 am

The main counter-point that I've got to Donnie's "get an 8" if you want a G80" is that the 8.6" G80 is a stronger unit than the 8" G80...

Also, on some vehicles, the G80 is called "posi-trac" and on others (the trucks), it's called "differential, auto-locking" or "differential, locking"

If it locks up 100% (which the G80 does), it's technically a "locker", whether it be a clutch-type locker (like the G80) or a dog-type locker, like the Detriot and lunchbox lockers...

A limited slip can be conical, clutch, or gear (or shop rags, in a pinch, if you live where I live), and they work exactly the opposite of how you'd want... When there's lots of traction, they are almost 100% locked, and when there's very little traction on one tire, they are almost completely open...

The G80 works exactly how an automatic REAL locker should, in a stock vehicle... It's completely open in normal driving. It doesn't scrub tires under power while turning. It locks up 100% when you need it. Yes, it's made for stock tires and power, and low traction situations, and yes, if you run larger tires and/or beat on it like a Detriot, it'll eventually break... Fact is, it's the best thing going, stock, without going to an ARB style like the Rubicons have...

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by fishsticks » Fri Jul 15, 2011 4:59 pm

bartonmd wrote:The main counter-point that I've got to Donnie's "get an 8" if you want a G80" is that the 8.6" G80 is a stronger unit than the 8" G80...



Can we sure that it's appreciably stronger? Has anyone bothered to look at them side by side?

The design issues with the G80 still exist in the 8.6" variety:
  • Since all the internals are slightly larger, I doubt the carrier walls are any thicker.
  • It still expects all torque to be held by two tiny spider gears when locked.
  • It still requires a ratchet/cam gear with ridiculously tiny teeth to hold pressure on the clutch plates.
  • It still requires wheelspin to engage, which shock loads the entire system every time it locks up.


Going 8.6 gets your a bigger R&P, larger bearing journals and stronger axles. But what good is that if the G80 is still the first/most likely point of failure?


The argument about whether the G80 is a real locker has been beat to death on the internet, so it's not worth rehashing here. I'll submit this for thought: There is no mechanical means of fully locking the axles together in the G80. The clutches, especially when worn in, tend to slip slightly even under full cam engagement, so the wheels do not turn at the same speed. Therefore they are not locked together.
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by snowmirage » Fri Jul 15, 2011 7:07 pm

I'm a bit confused .... or happily surprised? I'm not sure which

Finally remembered to go look in my glove box for codes to see which gear ratio I have. And this is what I found.

Image

I kind of assumed I had the lesser of the gear ratios (the 3.42, though in retro spec I have no idea what I was making that assumption on....)

And I certainly didnt think I had the G80...

but yet there in Column 3 Row 3 is "GT4" which based on the wise Fishsticks advice indicates I have the 3.73's

and more surprisingly in Column 4 Row 3 is "G80"

Now I really havent taking this thing offroad much. Once on a back road in the forest the first week I had it, slid off the trail and sank into some mud had to get a passerby to yank me out. Other than that I had it in the snow for one Upstate NY winter the year I got it. But I never recall hearing, feeling or otherwise anything that would have lead me to beleive I had anything but an open diff in the back.

Now granted a sticker is just a sticker. Maybe someone replaced the glove box lid for some reason before I bought it at 67,000 miles... who knows I guess the only way to know for sure is to go crack open the pumpkin.


*EDIT*

Just was snooping around and came across these two video's. I'm a very visual / hands-on learner so this helped me get the right picture in my head. I'll have to go see if I can find some sand or something to test it in..... but... hmmm could be hard to get my 31's spinning lol

http://www.youtube.com/watch?v=tTGZOJQQ ... re=related

http://www.youtube.com/watch?v=KbMZ9vcY ... re=related

If nothing else they should be a helpful reference for others.
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by Trail X » Sat Jul 16, 2011 1:32 am

fishsticks wrote:
  • It still expects all torque to be held by two tiny spider gears when locked.


Technically the spider gears are rendered useless when the clutches activate. The torque is transmitted through the carrier housing to the clutch plates, and then directly to the side gears. The clutch compression force is transmitted from the left side to the right via item 11, again rendering the slider gears useless.
Image

fishsticks wrote:The argument about whether the G80 is a real locker has been beat to death on the internet, so it's not worth rehashing here. I'll submit this for thought: There is no mechanical means of fully locking the axles together in the G80. The clutches, especially when worn in, tend to slip slightly even under full cam engagement, so the wheels do not turn at the same speed. Therefore they are not locked together.


Would you then, by extension, consider any rear locker that operates using clutches not to be a locker? The Auburn Ected uses clutches in the exact same manner as the G80.
Image

snowmirage wrote:Now I really havent taking this thing offroad much. Once on a back road in the forest the first week I had it, slid off the trail and sank into some mud had to get a passerby to yank me out. Other than that I had it in the snow for one Upstate NY winter the year I got it. But I never recall hearing, feeling or otherwise anything that would have lead me to beleive I had anything but an open diff in the back.

Now granted a sticker is just a sticker. Maybe someone replaced the glove box lid for some reason before I bought it at 67,000 miles... who knows I guess the only way to know for sure is to go crack open the pumpkin.


If you're really concerned, lift a rear wheel in the air, put your transfer case into neutral, then rotate the lifted wheel fast and see if it locks up.
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by fishsticks » Sat Jul 16, 2011 3:57 am

JamesDowning wrote:Technically the spider gears are rendered useless when the clutches activate. The torque is transmitted through the carrier housing to the clutch plates, and then directly to the side gears. The clutch compression force is transmitted from the left side to the right via item 11, again rendering the slider gears useless.


It may seem that way on paper. But many folks (myself and Teebes on here included) have found cracked spider gears in their G80s. My G80 failure stripped teeth off of the spiders, but still allowed me to drive forward on the rear axle until I lost traction with one wheel. Keep in mind this was with new clutches in mine. The clutch mechanism isn't able to hold the torque of the driveline by itself. The spiders are relied on heavily.

Would you then, by extension, consider any rear locker that operates using clutches not to be a locker? The Auburn Ected uses clutches in the exact same manner as the G80.
Image


The general consensus on Pirate seems to be that Ected's will slip one wheel under heavy loading. So I would say no. It's a very tight limited slip. There's apparently some concern about premature clutch wear for rigs that engage the Ected a lot as well. I honestly have no idea how prevalent that is though.

Me? I see spider gears and clutches in that schematic. Based on past experience, no way would I run one of those. I'm soured to the whole idea.

Here's a random thread, definitely not the only one: http://www.pirate4x4.com/forum/showthread.php?t=257518
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by janesy86 » Sat Jul 16, 2011 8:28 am

Yea I've read a few threads with people complaining about the Auburn Etched locker, can't say I chose one of those over anything else...
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by bartonmd » Sat Jul 16, 2011 11:51 am

fishsticks wrote:
bartonmd wrote:The main counter-point that I've got to Donnie's "get an 8" if you want a G80" is that the 8.6" G80 is a stronger unit than the 8" G80...



Can we sure that it's appreciably stronger? Has anyone bothered to look at them side by side?

The design issues with the G80 still exist in the 8.6" variety:
  • Since all the internals are slightly larger, I doubt the carrier walls are any thicker.
  • It still expects all torque to be held by two tiny spider gears when locked.
  • It still requires a ratchet/cam gear with ridiculously tiny teeth to hold pressure on the clutch plates.
  • It still requires wheelspin to engage, which shock loads the entire system every time it locks up.


Going 8.6 gets your a bigger R&P, larger bearing journals and stronger axles. But what good is that if the G80 is still the first/most likely point of failure?


I'm not saying the 8.6 G80 is bullet-proof, but they survive every day in 1/2 ton trucks that have 31" tires, and are 1000# heavier than us, and spin the tires more, and have more power (than you guys anyway), and are generally used heavier in stock form... Yes, there are failures on anything, but by and large, in stock form, the 8.6 G80 is appropriately sized and strong for a 1/2 ton truck.

... and yes, those small parts and gears are small because they can be... GM wouldn't have kept it this long if they were exploding all the time, and costing them a lot of warranty money... Yes, you see people break them, but the % actually isn't that high, and it's really low in stock form, as a % of the number of them out there...


The argument about whether the G80 is a real locker has been beat to death on the internet, so it's not worth rehashing here. I'll submit this for thought: There is no mechanical means of fully locking the axles together in the G80. The clutches, especially when worn in, tend to slip slightly even under full cam engagement, so the wheels do not turn at the same speed. Therefore they are not locked together.


There is really no way for that to happen... It either completely locks up, or the flyweight rod (or something else) breaks... If it's not 100% locked up, the cam keeps rotating, because the flyweight is still spinning, which causes the cam to ramp up even more... If the cam is 100% locked and the axles are still spinning different speeds (clutches worn out), something's going to give...

Only one side gets clutched to the carrier, so I think the spider gears do transfer load from the side gear that's locked to the carrier to the other one that's not... If you've broken spider gears, you weren't engaging it softly enough for your setup, and the conditions.

Yes, it's not a Detroit. Nobody is saying it is. What it is, is the best stock automatic locker going.

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by fishsticks » Sat Jul 16, 2011 12:47 pm

Nope it's not a Detroit. No one ever insinuated it was. Sure they live in thousands of full size trucks, 99.5% of which never leave pavement (and therefore hardly ever engage the G80). Most of these guys (I'm assuming) are serious enough about upgrades to actually get out there and use them. As frequency of use increases, so does the failure rate.

The first/most likely point of failure in the 8" or 8.6" is going to be the G80. So it makes no sense to upgrade to the 8.6" G80 for strength only... As I see nothing showing there is a significant difference in strength between the 8" and 8.6" G80s. That was my original point. Bill did it because his 8" exploded on him and he needed a replacement right then. I get that.

Some of these guys are talking about replacing a functioning differential. If the get a G80 and want/have to upgrade later, they then HAVE to do a full carrier replacement and resetup gears. That's a lot of money that they may not realize they're getting into.

Not to mention that 8" rears are a dime a dozen and 8.6's seem to be getting harder to find.

There is really no way for that to happen... It either completely locks up, or the flyweight rod (or something else) breaks... If it's not 100% locked up, the cam keeps rotating, because the flyweight is still spinning, which causes the cam to ramp up even more... If the cam is 100% locked and the axles are still spinning different speeds (clutches worn out), something's going to give...


Perhaps you've found the cause of the majority of ratchet failures out there.

Only one side gets clutched to the carrier, so I think the spider gears do transfer load from the side gear that's locked to the carrier to the other one that's not... If you've broken spider gears, you weren't engaging it softly enough for your setup, and the conditions.


I broke mine "bumping up" a rock on the rear. Sometimes you just need plain old inertia to get you over something. What does the G80 user do in that situation? Not climb the obstacle? That's no fun.
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by bartonmd » Sat Jul 16, 2011 1:04 pm

fishsticks wrote:Nope it's not a Detroit. No one ever insinuated it was. Sure they live in thousands of full size trucks, 99.5% of which never leave pavement (and therefore hardly ever engage the G80). Most of these guys (I'm assuming) are serious enough about upgrades to actually get out there and use them. As frequency of use increases, so does the failure rate.

The first/most likely point of failure in the 8" or 8.6" is going to be the G80. So it makes no sense to upgrade to the 8.6" G80 for strength only... As I see nothing showing there is a significant difference in strength between the 8" and 8.6" G80s. That was my original point. Bill did it because his 8" exploded on him and he needed a replacement right then. I get that.

Some of these guys are talking about replacing a functioning differential. If the get a G80 and want/have to upgrade later, they then HAVE to do a full carrier replacement and resetup gears. That's a lot of money that they may not realize they're getting into.

Not to mention that 8" rears are a dime a dozen and 8.6's seem to be getting harder to find.


I do agree that if one can swing the extra $200, get an open 8.6 and a lunchbox locker and be done with it...

The only reason I say the 8.6 G80 is stronger than the 8.0 is because Eaton says it's "heavy duty" and they do not say that about the 8.0 unit... Also, because the 8.0 is built for the TB, where the 8.6 is built for a full sized truck, which is heavier and has more torque (can get better gears)...

Perhaps you've found the cause of the majority of ratchet failures out there.


Yep. Well, that and just getting them spinning too fast when they engage, and breaking the parts from the impact...

I broke mine "bumping up" a rock on the rear. Sometimes you just need plain old inertia to get you over something. What does the G80 user do in that situation? Not climb the obstacle? That's no fun.


If you go up to it and spin enough to lock it up, if you keep a little bit of power on it, it'll stay locked up. I don't know about your specific situation, but I've done this with a fair amount of success...

Mike
bartonmd
Contributing Author & Off-Road Vendor
 
Posts: 4471
Joined: Wed Sep 09, 2009 9:35 am
Location: IN, Indianapolis
Name: Mike
Vehicle Year: 2007
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ G80
Rank: Offroad Rated

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