jscusmcvet
Explorer
So where di dyou find the SPID code? Gaining this info would make a great start point for those of us (you and me too!) new to these vehicles.
Got my new-to-me rig: '04 Suburban 1500 LT...
- Thread starter Martinjmpr
- Start date
Colorado_Outback
Adventurer
Nice looking rig! G80 is cool as long as it keeps doing its thing.. they are known in some circles as the gov bomb.
Here is some light reading on the subject I saved from another site.
LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION) #91-4-109
SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT - (SERVICE INFORMATION)
VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS
Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.
This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.
To correct this condition, drain and refill the rear axle with SAE 75W-90 GL5 (P/N 12378261). The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.VEHICLES/COMPONENTS INVOLVED: ----------------------------- Some light duty trucks equipped with locking rear axles, RPO G80.
SERVICE PARTS INFORMATION:
Part Number Description ----------- ------------------ 12678261 Lubricant, Rear Axle (1 litre)
Parts are currently available through CANSPO.
WARRANTY INFORMATION:
As specified in Light Duty Truck Maintenance Schedules, locking rear axle fluid drain and refill is required owner maintenance at the first engine oil change. Failure to drain and refill the rear axle as specified may contribute to a later axle chatter condition. Refer to the appropriate Light Duty Truck Maintenance Schedule or service manual, section OB, for further details on change intervals.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
© Copyright General Motors Corporation. All Rights Reserved.
What Eaten says.....
"From Mr. Ralph Holmquist of Eaton, the maker of the locking differential:
"The maintenance schedule for the rear axle was developed by American Axle &
Manufacturing and GM truck based on multiple tests. The Eaton locker does
not require additional maintenance nor does it add heat to the lube. The
lube will darken due to the carbon wear on the clutch surfaces, much the
same as a disc brake pad & rotor. This does not damage axle components such
as seals or bearings. However, a new axle can produce excessive
temperatures (plus 350 degrees F) due to the ring & pinion breaking in that
will break the lube additives down. Avoid high loads, trailer towing and
high speed extended driving during the initial break in of the vehicle.
After the break in period axle temps will level at a much lower figure.
Lube changes are a good idea because the additives are replenished and
contaminates such as casting sand are eliminated. The axle is filled at the
factory with a synthetic 75w90 GL5 rating made by Texaco under part # 2276.
The GM service # is 12378261. This is the only lube we have done extensive
testing with to insure locker compatibility. The only negative to using one
of these other lubes is an increased potential for clutch chatter. This
really doesn't hurt anything and can be corrected by changing the lube. I
noticed in the latest GM owners manual the term "or equivalent" when
referring to the lube specification. Look for a GL5 rating on the bottle to
make sure the ring & pinion, seals & bearings are protected. Limited slip additive is not needed."The following information outlines the type of
rear axle lubrication utilized in GM Truck axles.
I. Fluid Type
II. The 1500, 2500 and 3500 GMT 800 Trucks utilize SAE 75W-90 Synthetic Axle Lubricant. The GM part number is 12378261 and the specification is 9986115.
How a G80 works...
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 open diff 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.
Here is some light reading on the subject I saved from another site.
LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION) #91-4-109
SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT - (SERVICE INFORMATION)
VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS
Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.
This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.
To correct this condition, drain and refill the rear axle with SAE 75W-90 GL5 (P/N 12378261). The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.VEHICLES/COMPONENTS INVOLVED: ----------------------------- Some light duty trucks equipped with locking rear axles, RPO G80.
SERVICE PARTS INFORMATION:
Part Number Description ----------- ------------------ 12678261 Lubricant, Rear Axle (1 litre)
Parts are currently available through CANSPO.
WARRANTY INFORMATION:
As specified in Light Duty Truck Maintenance Schedules, locking rear axle fluid drain and refill is required owner maintenance at the first engine oil change. Failure to drain and refill the rear axle as specified may contribute to a later axle chatter condition. Refer to the appropriate Light Duty Truck Maintenance Schedule or service manual, section OB, for further details on change intervals.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
© Copyright General Motors Corporation. All Rights Reserved.
What Eaten says.....
"From Mr. Ralph Holmquist of Eaton, the maker of the locking differential:
"The maintenance schedule for the rear axle was developed by American Axle &
Manufacturing and GM truck based on multiple tests. The Eaton locker does
not require additional maintenance nor does it add heat to the lube. The
lube will darken due to the carbon wear on the clutch surfaces, much the
same as a disc brake pad & rotor. This does not damage axle components such
as seals or bearings. However, a new axle can produce excessive
temperatures (plus 350 degrees F) due to the ring & pinion breaking in that
will break the lube additives down. Avoid high loads, trailer towing and
high speed extended driving during the initial break in of the vehicle.
After the break in period axle temps will level at a much lower figure.
Lube changes are a good idea because the additives are replenished and
contaminates such as casting sand are eliminated. The axle is filled at the
factory with a synthetic 75w90 GL5 rating made by Texaco under part # 2276.
The GM service # is 12378261. This is the only lube we have done extensive
testing with to insure locker compatibility. The only negative to using one
of these other lubes is an increased potential for clutch chatter. This
really doesn't hurt anything and can be corrected by changing the lube. I
noticed in the latest GM owners manual the term "or equivalent" when
referring to the lube specification. Look for a GL5 rating on the bottle to
make sure the ring & pinion, seals & bearings are protected. Limited slip additive is not needed."The following information outlines the type of
rear axle lubrication utilized in GM Truck axles.
I. Fluid Type
II. The 1500, 2500 and 3500 GMT 800 Trucks utilize SAE 75W-90 Synthetic Axle Lubricant. The GM part number is 12378261 and the specification is 9986115.
How a G80 works...
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 open diff 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.
Martinjmpr
Wiffleball Batter
.
Sorry, are you asking where to find the codes in a vehicle or where to find the index that shows what they mean?
.
For the first question there is a sticker inside the glovebox that says "do not remove" and has all these codes on it.
.
For the second question follow the link in post # 15 above and click on the PDF link. It goes to a 188 page PDF file that lists every GM RPO code.
jscusmcvet
Explorer
Thanks Martin.. I meant the sticker... looks like it will be a big help in understanding the 91 I just bought. Appreciate the info.
Martinjmpr
Wiffleball Batter
I don't know if your 91 will have the sticker, as I'm not sure when that started but it's a good place to look.
justcuz
Explorer
Yes the 1991 will have the glovebox sticker. Great write up with the G80 info. An easier way is to go to YouTube and watch the G80 videos, the visuals will tie in with the write up nicely.
My 2000 has H2 rear springs, will get Ford torsion bar keys and I run 285/75x16 tires. I have 3.73 gears also and had a G80.
My wife and daughter have managed to blow up every G80 we ever had. Gradually increasing the throttle application in low traction conditions is the key, not hammering the throttle like my girls do!
The 130" WB is the same as a long bed standard cab pickup.
You also should have a hydro boost power brake system.
Chevy leather, like most others will crack after a while. The secret to keeping it nice is liberal applications of saddle soap to clean it and keep it soft. I do mine 4 times a year.
My 2000 has H2 rear springs, will get Ford torsion bar keys and I run 285/75x16 tires. I have 3.73 gears also and had a G80.
My wife and daughter have managed to blow up every G80 we ever had. Gradually increasing the throttle application in low traction conditions is the key, not hammering the throttle like my girls do!
The 130" WB is the same as a long bed standard cab pickup.
You also should have a hydro boost power brake system.
Chevy leather, like most others will crack after a while. The secret to keeping it nice is liberal applications of saddle soap to clean it and keep it soft. I do mine 4 times a year.
4x4x4doors
Explorer
Nice ride. Congrats!
Expedition white? You disappoint me.
Expedition white? You disappoint me.
Colorado_Outback
Adventurer
On the topic of RPO stickers, does anyone know if there is a reverse lookup of some kind, maybe by vin? My 94 had a hand full of lug nuts in the glove box for a long time so the sticker is completely gone.
Martinjmpr
Wiffleball Batter
The only one I know of is a pay site. Apparently it used to be free but is no longer.
.
http://www.compnine.com/vid.php
Martinjmpr
Wiffleball Batter
.Nice ride. Congrats!
Expedition white? You disappoint me.
Yeah, yeah. Well, it was that or black and I wasn't going to get a black vehicle.
Martinjmpr
Wiffleball Batter
Better pics, finally
Well it's still colder than crap outside but I managed to take a few better pics with a real camera instead of my phone:
.
.
Flag included because 'Merica! :elkgrin:
.
.
Nice interior:
.
.
More storage behind the THIRD row than my 4runner had behind its second:
.
.
This is a neat feature. Not the 1/3 - 2/3 split bench, I'm talking about the little swinging "platform" that covers the 3rd row seat footwell. In this position it's flipped up against the back of the 2nd row seat, exposing the footwell and making the 3rd row more comfortable for 3rd row passengers...
.
.
...But flip it down and it covers the footwell, giving a nice, flat load deck when the 3rd row is removed and the 2nd row either in place or folded down:
.
.
Pretty clever and useful, I have to say. The lack of flat load decks on some SUVs (notably on both of my 4runners) is a pet peeve of mine.
Well it's still colder than crap outside but I managed to take a few better pics with a real camera instead of my phone:
.
.
Flag included because 'Merica! :elkgrin:
.
.
Nice interior:
.
.
More storage behind the THIRD row than my 4runner had behind its second:
.
.
This is a neat feature. Not the 1/3 - 2/3 split bench, I'm talking about the little swinging "platform" that covers the 3rd row seat footwell. In this position it's flipped up against the back of the 2nd row seat, exposing the footwell and making the 3rd row more comfortable for 3rd row passengers...
.
.
...But flip it down and it covers the footwell, giving a nice, flat load deck when the 3rd row is removed and the 2nd row either in place or folded down:
.
.
Pretty clever and useful, I have to say. The lack of flat load decks on some SUVs (notably on both of my 4runners) is a pet peeve of mine.
Martinjmpr
Wiffleball Batter
Plans: This will not be much of a "build" at all as the truck is fairly ready for its primary duties as a family truckster/tow vehicle right now.
.
I do have a "punch list" of things that need to be done though:
.
First off is to get the trailer brake control wired up. The "pigtail" is in the glove box, looks like it's never been used so I'll have to have that wired in, then I'll plug in the brake controller and mount it to the dash below the steering wheel.
.
2nd "critical" need is to get it set up so we can listen to the iPod. Factory stereo has XM1 and XM2 and from what I've read I can "tap into" the XM connection to put in a standard 3.5mm audio plug, that way we can listen to an iPod or iPhone. Of course I could always replace the head unit but to be honest, I kind of like the factory head unit on this, except for not having BT and an aux input.
.
After that there are some minor repairs that need to be done, the kind of thing that, honestly, I expect on a 12-year-old, 136k mile vehicle: Possible broken seat motor in the driver's seat (will go back and forth and recline but won't go up and down), dim PRNDL light (this is apparently a known problem on these GMT800 trucks and requires a resistor to be resoldered.)
.
It would be nice to also wire in my Scangauge II. Even though the DIC (Drivers Information Center) on the dashboard gives me things like instant and average MPG, the nice thing about the SG is that it will show me transmission temps, too.
.
Way "down the road" it might be nice to wire in a dual battery setup, although I'm not sure there's room even under that gargantuan hood. With 4 12v power plugs (2 in the dash, 1 in the center console facing towards the 2nd row seat and one in the cargo area) I should have plenty of places to hook up all my electric gadgets. More tiedowns in the cargo compartment would also be nice. A mild lift (keys and Z71 springs) is also a possibility and if I do that I may go to 33" tires (currently its shod with 265/70/17 Kelly Safari ATRs. I don't know much about them but they're in decent shape and certainly performed well enough in our recent 10" snow storm that I'm inclined to at least keep them until the Spring.)
.
Beyond that? Just a lot of traveling and exploring the country. We already have plans to visit Washington (state), Montana, Yellowstone NP, Sturgis SD (Liz will drive and I'll ride my Triumph) and a whole bunch of trips within CO. I'm thinking this beast will be a great traveling vehicle as long as I can convince my wife not to fill it with too much crap (I know, probably useless.)
.
I do have a "punch list" of things that need to be done though:
.
First off is to get the trailer brake control wired up. The "pigtail" is in the glove box, looks like it's never been used so I'll have to have that wired in, then I'll plug in the brake controller and mount it to the dash below the steering wheel.
.
2nd "critical" need is to get it set up so we can listen to the iPod. Factory stereo has XM1 and XM2 and from what I've read I can "tap into" the XM connection to put in a standard 3.5mm audio plug, that way we can listen to an iPod or iPhone. Of course I could always replace the head unit but to be honest, I kind of like the factory head unit on this, except for not having BT and an aux input.
.
After that there are some minor repairs that need to be done, the kind of thing that, honestly, I expect on a 12-year-old, 136k mile vehicle: Possible broken seat motor in the driver's seat (will go back and forth and recline but won't go up and down), dim PRNDL light (this is apparently a known problem on these GMT800 trucks and requires a resistor to be resoldered.)
.
It would be nice to also wire in my Scangauge II. Even though the DIC (Drivers Information Center) on the dashboard gives me things like instant and average MPG, the nice thing about the SG is that it will show me transmission temps, too.
.
Way "down the road" it might be nice to wire in a dual battery setup, although I'm not sure there's room even under that gargantuan hood. With 4 12v power plugs (2 in the dash, 1 in the center console facing towards the 2nd row seat and one in the cargo area) I should have plenty of places to hook up all my electric gadgets. More tiedowns in the cargo compartment would also be nice. A mild lift (keys and Z71 springs) is also a possibility and if I do that I may go to 33" tires (currently its shod with 265/70/17 Kelly Safari ATRs. I don't know much about them but they're in decent shape and certainly performed well enough in our recent 10" snow storm that I'm inclined to at least keep them until the Spring.)
.
Beyond that? Just a lot of traveling and exploring the country. We already have plans to visit Washington (state), Montana, Yellowstone NP, Sturgis SD (Liz will drive and I'll ride my Triumph) and a whole bunch of trips within CO. I'm thinking this beast will be a great traveling vehicle as long as I can convince my wife not to fill it with too much crap (I know, probably useless.)
justcuz
Explorer
You can get a trailer plug that plugs right into the tail light loom, no splicing required. Also most tow packages had a 7 pin I think plug pre wired next to the hitch. I thought the trailer brake was part of the 7 pin receiver?
Looks nice and clean, obviously a well cared for Suburban.
Looks nice and clean, obviously a well cared for Suburban.
ZMagic97
Explorer
This is a really easy fix. I did it in an hour start to finish.
Here's a good link: http://www.silveradoss.com/forums/topic/62576-dim-or-dark-prnd21-fix/
I also added solder to some points that seemed like they could use it.
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