I have the build sheet for this truck, but alas - no G80 locker. Can someone
please tell me what other rear end options were available for a Z71 4x4 of
Surely GM would not build a 4x4 truck without at least a LSD rear end?! Even
my '92 Nissan 4x4 had a limited slip rear axle. Please tell me this is not
an open differential!
BTW, I have not tried jacking up the rear and turning one wheel to see what
happens - yet.
Can anyone shed light on this issue?
I would "assume" so (geeze - I do know what trouble that word can cause).
Did not actually try. Was performing this "test" by myself.
When trying this, I would suddenly change directions on the one I was moving
by hand. When I did so, the other side would slow to a stop then change
directions. Either way, the opposite side was definitely moving in the
opposite direction from the one I was physically rotating.
The G80 is a LSD that they call a "locker" but a true locker do not
use friction clutches to lock up like G80 does,(calling it a locker is
a great sales promo/gimic) it is mechanical and cannot slip unless
something breaks while a G80 will slip when its torque limit is
reached and if reach a lot for any period od time it will toast and
not longer be a LSD as many offroads have found out the hard way over
Not this again, its only an LSD in your head, everyone else knows the
difference. Yes it may have a upper limit where it breaks loose to prevent
damage but that is not how an LSD works, when the g80 is engaged it is
locked, when a LSD engaged is still allows slip, its like comparing a
manual transmission clutch with a torque converter.
I dont know what the hell Snoball is rambling about (who the hell ever
does) but this is how it is described by GM word for word:
1998 Chevrolet/Geo Chevy C Pickup - 2WD
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 case only
* Differential pinion gear shaft lock bolt - 1 piece case only
* 2 clutch discs 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 locking 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 2 ways. First 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 10.5 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.
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 10.5 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 side gears from being
held to the differential case.
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 100 RPM 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 cam side
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 its 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 cam
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. The 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 32 km/h (20 mph) and
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.
Locking Differential Torque-Limiting Disc
The locking differential design was modified in mid-1986 to include a
load-limiting feature to reduce the chance of breaking an axle shaft
under abusive driving conditions. The number of tangs on the energizing
disc in the left-hand clutch pack was reduced allowing these tangs to
shear in the event of a high-torque engagement of the differential
At the time of failure of the load-limiting disc, there will be a loud
bang in the rear axle and the differential will operate as a standard
differential with some limited-slip action of the clutch packs at low
The service procedure, when the disc tangs shear, involves replacing the
left-hand clutch plates and the wave spring. It is also necessary to
examine the axle shafts for twisting because at high torques it is
possible to no only shear the load-limiting disc, but to also twist the
The Snoball Defense System.
Sno on brakes:
You just do not get it do you??? Lockers DO NOT uses fricton clutches
to lock, they use mechanical locks that CANNOT slip. The G80 can and
will if enough torque is applied and that is easy to do with oversized
tires. Eaton uses a cam to preload engagement a bit to make it appear
to be a locker but it is not and also it blocks operation above 20 MPH
oe so so above that it is basicallt a open diff with a little bit a
LSD from oil shearing in clutches. Also a classic LSD do basically
work the same as they all have their break limit and some even
increase preload and tighten up even more under torque (like dana
PowerLoc LSD) The G80 is a locker in name only and is going to be
phased out in future and replaced with a more conventional LSD design.
You don't get it, clutches can not slip, just like the clutch in a manual
transmission. You can't make up your own definition for something just
because you don't agree with it. The G80 does not slip when operating,
therefore it is not a limited slip. Note slip is the operative word,
limited slip does slip some, g80 does not.
I have to disagree on this one. My G-80 with right tire in mud (deep mud)
left on road surface. It started spinning the right wheel, then it clunked
in and pulled out using only the left tire that was on road surface. If it
weren't for the truck weighing over 8,000 lbs. and having a 12,000 + lbs.
trailer fully loaded while this happened... (that's over 20,000 lbs.) If
that wasn't locked then I better go to Church and thank the guy upstairs for
making it get me out of that mess...
If there is not G80 code, it does not likely have a GovLoc in it. It
was not standard then and standard today only with very few models.
Myself I am not a fan of it for my usage (watch the peanut gallery
pipe in). I have been stuck good twice in last 15 years and both
times LSD would not have made any difference at all because all four
tires where mostly spining anyway. The reason I am not fond of it is
because it makes vehicle more prone to fishtale on ice and I run a few
plow trucks and have for many years and directional control is VERY
important. Contray to poular belief, a open diff sends the same amount
of torque to both wheels, no more, no less as it can do nothing else.
A LSD can send more torque to one axle than the other.
Care to explain "all four tires were mostly spinning" I thought you were a
fan of open dif's.
Why am I not surprised that you don't use a ls on the rear. I'm trying to
think of who else I know that prefer's a open dif on a 4X4 for snow plowing.
If you get the snow plow prep, I believe it comes with the ls. Not as a part
of the pkg but on the truck.
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