g80

[fritzi091308]

My trailblazer came with the 3.73/ g80 but had the rear axle replace. New axle is the 3.73 im wondering if there is any way to check if the new one has th g80.

[Bthracer21]

If it was just the axle replaced then the G80 should still be there... But if the whole rear was replaced, then I dunno. Then its a matter of part numbers

[AlekG]

There is no part number externally anywhere that would tell you if housing has the g80 in it (assuming that you replaced the entire housing).

So the only way to be sure is to open it up.

Unless you can find some ice and put one wheel on it and the other off. A little bit of gas and you can tell right away.

AG

[fritzi091308]

Idk i believe it was just the axle. the dealer gave me the service recipt and thats all it shows for parts.

[fritzi091308]

I guess i'll find out soon suppose to snow in WI

[RayVoy]

The key, is probably the cost to repair. A few hundred $ would replace one of the rear axle shafts, a much larger bill would probably be the cost of a new rear axle assemble (housing, axles, pumpkin).

BTW, if this was just repaired a new axle housing would look new. The old one would be rusty.

[fritzi091308]

The axle is outta a 04 tb

[UTIpastudent]

Really simple test. Put the axle assy up in the air and rotate one tire. Does the opposite tire spin the the same direction that you're rotating the one tire? If so you have a G80!! If not then sorry :)

[85vette]

Actually if you do the above test and both tires spin the same direction, you have a posi-trac. Something only the SS Trailblazer has. The G80 is an open carrier with a locker (govlock). Better yet, especially if you don't happen to have a lift in your garage, put one tire on the grass, the other on the asphalt, and floor it....

[UTIpastudent]

Well i mean...if you have a floor jack it's simple enough...

[the roadie]

Really simple test. Put the axle assy up in the air and rotate one tire. Does the opposite tire spin the the same direction that you're rotating the one tire? If so you have a G80!! If not then sorry :)Our g80 doesn't work that way. There's an RPM threshold you need to get to, and I'm pretty sure hand-spinning can't get to 200 RPM. Supporting the frame on a jack stand on one side is one trick, or my favorite safe trick of freezing some water in a cookie sheet, then placing that under one rear tire. Then trying to drive off it.

Never use full throttle on a g80 - it could break if it engages with a lot of energy behind it.

[UTIpastudent]

I was under the impression that our lockers also limited the amount of slippage between each wheel with a series of clutch plates at each side of the differential case, so that even without the rpm threshold achieved some limited slip would occur.

[85vette]

Our g80 doesn't work that way. There's an RPM threshold you need to get to, and I'm pretty sure hand-spinning can't get to 200 RPM. Supporting the frame on a jack stand on one side is one trick, or my favorite safe trick of freezing some water in a cookie sheet, then placing that under one rear tire. Then trying to drive off it.

Never use full throttle on a g80 - it could break if it engages with a lot of energy behind it.

From a dead stop, with all the factory installed torque management, that shouldn't be an issue. If you have a tune I would be concerned. If you are spinning both wheels in the grass and then contact pavement with one wheel, this can (and probably will) cause breakage.

I was under the impression that our lockers also limited the amount of slippage between each wheel with a series of clutch plates at each side of the differential case, so that even without the rpm threshold achieved some limited slip would occur.


No clutches.:nono:

[UTIpastudent]

:bonk: my bad! Guess i had the wrong impression of the operation.

[the roadie]

The offroad forum gurus know all ... tell all....

http://48facets.files.wordpress.com/2007/06/carnac.jpg

It also helps to own a factory service manual with the detailed theories of operation of all the systems. :woot:

[UTIpastudent]

Ok i've looked into this a little further and this information comes directly from the manufacturer of the G80.

Differential Assembly: Description and Operation
Drive Axle-Locking/Limited Slip
Locking Differential Description and Operation
The Locking differential consists of the following components:
-Differential case-1 or 2 piece
-Locking differential spider-2 piece case only
-Pinion gear shaft-1 piece only
-Differential gear shaft lock bolt-1 piece only
-2 clutch disc sets
-Locking differential side gear
-Thrust block
-Locking Differential clutch disc guides
-Differential side gear shim
-Locking differential clutch disc thrust washer
-Locking differential governor
-Latching bracket
-Cam Plate assembly
-Differential pinion gears
-Differential pinion gear thrust washers
The optional differential (RPO G80) enhances the traction capability of the rear axle by combining the characteristics of a limited-slip differential and the ability of the axle shafts to "lock" together when uneven traction surfaces exist. The differential accomplishes this in two ways. Fist by having a series of clutch plates at each side of the differential case to limit the amount of slippage between each wheel. Second, by using a mechanical locking mechanism to stop the rotation of the right differential side gear, or the left differential side gear on the 8.0 or 8.6 inch axle, in order to transfer the rotating torque of the wheel without traction to the wheel with traction. Each of these functions occur under different conditions.

Limited-Slip Function:
Under normal conditions, when the differential is not locked, a small amount of limited-slip action occurs. The gear separating force developed in the right-hand (left hand side on the 8.6 inch axle) clutch pack is primarily responsible for this.

The operation of how the limited-slip function of the unit works can be explained when the vehicle makes a right-hand turn. Since the left wheel travels farther than the right wheel, it must rotate faster than the ring gear and differential case assembly. This results in the left axle and left side gear rotating faster than the differential case. The faster rotation of the left-side gear causes the pinion gears to rotate on the pinion shaft. This causes the right-side gear to rotate slower than the differential case.

Although the side gear spreading force produced by the pinion gears compresses the clutch packs, primarily the right side, the friction between the tires and the road surface is sufficient to overcome the friction of the clutch packs. This prevents the gears from being held to the differential case.

Locking Function:
Locking action occurs through the use of some special parts:
-A governor mechanism with 2 flyweights
-a latching bracket
-the left side cam plate and cam side gear
When the wheel-to-wheel speed difference is 100RPM or more, the flyweights of the governor will fling out and one of them will contact an edge of the latching bracket. This happens because the left side cam gear and cam plate are rotating at a speed different, either slower or faster, than that of the ring gear and differential case assembly. The cam plate has teeth on its outer diameter surface in mesh with teeth on the shaft of the governor.

As the side gear rotates at a speed different than that of the differential case, the shaft of the governor rotates with enough speed to force the flyweights outward against spring tension. One of the flyweights catches its edge on the closest edge of the latching bracket, which is stationary in the differential case. This latching process triggers a chain of events.

When the governor latches, it stops rotating. A small friction clutch inside the governor allows rotation, with resistance, of the governor shaft while one flyweight is held to the differential case through the latching bracket. The purpose of the governor's latching action is to slow the rotation of the cam plate as compared to the cam side gear. This will cause the cam plate to move out of it's detent position.

The cam plate normally is held in its detent position by a small wave spring and detent humps resting in matching notches of the cam side gear. At this point, the ramps of the cam plate ride up on the ramps of the cam side gear, and the cam plate compresses the left clutch pack with a self-energizing action.

As the left clutch pack is compressed , it pushes the cam plate and side gear slightly toward the right side of the differential case. This movement of the cam side gear pushes the thrust block which compresses the right-hand side gear clutch pack. At this point, the force of the self-energizing clutches and the side gear separating force combine to hold the side gears to the differential case in the locking stage.

The entire locking process occurs in less than 1 second. The process works with either the left or right wheel spinning, due to the design of the governor and cam mechanism. A torque reversal of any kind will unlatch the governor, causing the cam plate to ride back down to its detent position. Cornering or deceleration during a transmission shift will cause a torque reversal of this type. The differential unit returns to its limited slip function.

The self-energizing process would not occur if it were not for the action of one of the left clutch discs. This energizing disc provides the holding force of the ramping action to occur. It is the only disc which is splined to the cam plate itself. Te other splined discs fit on the cam side gear.

If the rotating speed of the ring gear and differential case assembly is high enough, the latching bracket will pivot due to centrifugal force. This will move the flyweights so that no locking is permitted. During vehicle driving, this happens at approximately 32km/h (20mph) ad continues at faster speeds.

When comparing the effectiveness of the locking differential, in terms of percent-of-grade capability to open and limited-slip units, the locking differential has nearly 3 times the potential of the limited-slip unit under the same conditions.



in essence.........Locking?LIMITED SLIP describes the G80!





and i couldn't even copy and paste all that in...stupid text documents...

[UTIpastudent]

the question mark an the end is supposed to be a slash Locking/LIMITED SLIP

[the roadie]

You found the mother lode of descriptions, all right. What they don't say is that the "small" amount of slip limiting that the wimpy clutch plates provide is really quite useless. Much less than in a non-locking limited slip unit that's designed that way. Our slip limiting is an accidental side effect, compared to the SS rear end that has real LS action, and no locking.

Without the locker, hill climbs like this would be totally impossible.

http://www.youtube.com/watch?v=24SwmSN0-bI

[UTIpastudent]

Nice vid! But to clarify due to this "wimpy slip limiting" side effect the wheels should rotate in the same direction when one is spun and the axle is in the air.

[the roadie]

I never tried it. You could.

[UTIpastudent]

ok to clarify further. The tires DO spin in the same direction when one is spun and the axle is up the in air.:raspberry

[the roadie]

OK. We'll add you to the rotation of folks who HAVE to answer questions from newbs. Will be nice to share the workload. You're on deck for the next one who asks if 31's will fit without spacers. :hail:

[UTIpastudent]

:bonk::duh: NO ROADIE!!! NO!!! I TAKE IT ALL BACK!! PLEASE NO!!! LMAO:thumbsup:

[petevw]

:bonk::duh: NO ROADIE!!! NO!!! I TAKE IT ALL BACK!! PLEASE NO!!! LMAO:thumbsup:

NOOOO......no taking it back. Everybody wants to be a "veteran" on here and show everybody how much they know, so now it's YOUR turn w/ the Newb's.
:raspberry :laugh:

[UTIpastudent]

Wait so is this official? :D

[petevw]

Wait so is this official? :D
Yessir...tag, your it! :woohoo: No more newb's for us for a while :woohoo:

[the roadie]

Unless you tell 'em something totally wrong, like they can still get in the skid plate GB, or it's easy to change the transfer case fluid. Then we slap the mallrated sticker on ya, shave your dog's butt and make him walk backwards.

[UTIpastudent]

:woohoo: Awesome! So i guess i can't put up those pictures of my truck climbing the curbs now? j/k :woot: Thanks!