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What kind of diff do I have?

85K views 23 replies 8 participants last post by  Teletoby 
#1 ·
Can someone decode my VIN for the differential RPO?

1GTEC19T64Z332428
 
#5 ·
99chevyz71 said:
GU6 AXLE,REAR,3.42 RATIO 3.42R(GU6)
G80 AXLE,REAR,POSITRACTION,LIMITED SLIP POSITRACTION L/SLIP R/AXL(G80)
Are you saying that my VIN says I have the Eaton G80 rear diff? What throws me off is that every RPO reference to G80 is a gov lock, locking rear diff. This says limited slip. Limited slip and lockers are completely different. Thank you very much for the help.

Well this opens up a whole new can-o-worms 'cause by rear end certainly does not behave like a locker read diff. Last time I tried to get up the in-laws icy driveway it sure acted like an open diff.

Anyone go any idears or info on SBs for the Eaton G80? I saw one SB that said the G80 oil needs to be serviced. (drumming fingers :roll: )
 
#6 ·
All diffs need their fluids changed now and then. How many miles on the truck?

The G80 won't lock if you are spinning the wheels too fast. It keeps the locker from engaging at speeds above 20mph or so (might be a touch lower). So don't spin too fast and see if it will lock.
 
#7 ·
Hey Wingnut
I looked up your VIN and 99chevyz71 is right. Your truck has the 3.42 ratio (GU6) with a limited slip diff.(G80). The difference between a limited slip and "Locker" is a limited slip is a spring loaded clutch arrangement in the differential that sorta locks up both rear wheels. "Lockers" have an arrangement that truly locks both rear axles together, up to a certain load point. I have a fairly steep driveway, and when it's snowy/icy I have to put my truck in Auto 4 to get up into the garage otherwise I sit there and spin. Also on oil changes; because the G80 has clutches, I have changed the oil and use Red Line Synthetic 75W90 with a friction modifier. I found that it works great and the rear end doesn't chatter around corners. Hope this helps.
 
#8 ·
Well this answers a lot. Kudos! I was mistaken to thing that RPO G80 was for the Eaton Gov Locker; not so evidently.

This will drive my decision to get an on command locker. I'm not happy with the limited slip; many of the places I go or tow involve steep icy roads and muddy paddocks at the race tracks. I have been looking at the Eaton Electric locker and I think that the E-locker with the BF Goodrich All Terrain T/As will answer the mail. Again, thanks for the help.
 
#9 ·
You can't go wrong with an Eaton (not biased becasue I work on Eaton pumps) :D Once the factory posi in my drag car gives up the ghost I'll be looking at an Eaton or Auburn Gear locker too!
 
#10 ·
I'm almost certain that the G80 is indeed an Eaton locker. I had the rear diff fluid changed and there was no friction modifier added. I've always assumed that GM's RPO description was just off. There are real limited slips diffs in GM passenger cars, etc. (ie, clutch plates, etc.) but I've always believed the G80 is an Eaton locker (and seems to be just that on my Silverado).
 
#11 ·
jreagan said:
I'm almost certain that the G80 is indeed an Eaton locker. I had the rear diff fluid changed and there was no friction modifier added. I've always assumed that GM's RPO description was just off. There are real limited slips diffs in GM passenger cars, etc. (ie, clutch plates, etc.) but I've always believed the G80 is an Eaton locker (and seems to be just that on my Silverado).
I've looked at the Eaton site and vendors who sell Eaton diffs. Nowhere does Eaton or the vendors call the Eaton mechanical locker a G80. I think the Eaton mechanical locker has picked up the G80 badge because og the GM RPO assignment. I don't know if the Eaton mech lockers were offered in 2004. So G80 in that year may heve meant the lim/slip diff.
 
#12 ·
I've done a little research and found this on Eatons site "The Eaton mechanical locking differentials were the first to be offered as an option to pickup drivers and today it is known around the world simply by the GM option code G80. This automatic unit, available as standard and optional equipment for rear drive and 4-wheel drive vehicles, makes traction problems a thing of the past."
That said, I guess you can call the G80 a "modified" locker as a true locking diff will have bad street manners and hop, pop and bang around corners. That's why drag racers like them, they lock both axles solid with NO slip. From the GM 2003 Service Manual,The G80 locking differential uses multi-disc clutch packs and a speed sensitive engagement mechanism that will lock both wheels together if 1 wheel spins excessively during SLOW vehicle operation. At vehcile speed above 20 MPH the latching bracket overcomes a spring preload and swings away from the flyweights. At this speed the diff is designed not to lock since added traction is generally not needed.
 
#13 ·
Once and for all, G80 in a truck is a mechanical locking differential made by Eaton and exclusive to GM trucks. Limited slip differentials are normally installed in rear wheel drive cars like the Cadillac CTS-V, Camaro and Corvette.

Btw - Both carry the G80 option code.

The Eaton locker in the trucks goes back to at least 1988 as I have a service bulletin that mentions it and it have quoted it below.

From a Cadillac Service Bulletin
Models: 2003-2010 Cadillac CTS, Sport Wagon (Including V-Series and Export)
2004-2009 Cadillac SRX (Including Export)
2005-2010 Cadillac STS (Including V-Series and Export)
Equipped with Limited Slip Differential (RPO G80)
From a truck service bulletin
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.


Btw - I have both G80's, in the 2010 GMC and in the 2009 CTS4 wish it was a V
 
#14 ·
Z15 said:
Once and for all, G80 in a truck is a mechanical locking differential made by Eaton and exclusive to GM trucks. Limited slip differentials are normally installed in rear wheel drive cars like the Cadillac CTS-V, Camaro and Corvette.
Got it Mike,

Earlier poster said my VIN was decoded as a G80 (lim slip). I'm going to get a second opinion on my VIN. If a dealer says my VIN has the G80, then I'll consider the issue settled.
 
#15 ·
I was not jumping on you but trying to correct misinformation. There are often arguments over this in forums where some insist its a limited slip. I have even encountered some GM techs that do not know there is a difference, especially if they are not skilled in differentials. Believe me, I had to stop them when installing AMSOIL in my 2004 GMC because they were going to install an additive. I observed the install tech at the parts counter getting a bottle of additive and I stopped him and that po'd him off. That's the GM dealer and a tech with nearly 20 yrs of experience who was giving me the hard time.

The axle is not coded in the VIN BUT a GM can run a "build out" of any vehicle using the VIN. Ask them for a paper copy of that, don't take their word.

Just fyi - These new trucks I had were always ordered with the G80 locker
1987 Silverado regcab (my last 4x2)
1989 Silverado regcab
1992 Silverado Z71 Ecab
1996 Silverado Z71 ecab
1999 GMC Sierra Z71 ecab
2001 GMC Sierra Z71 ecab <---waited months to get this truck due to G80 on constraint
2004 GMC Sierra Z71 ecab
2008 GMC Sierra Z71 ecab
2010 GMC Sierra Z71 ecab

These cars had the G80 limited slip
2002 Trans Am WS6 LS1
2005 Cadillac CTS
2009 Cadillac CTS4

This pic below is from a 2003 GMC brochure. I had a 2003 GMC Sierra SLT Ext Cab Z71.
 
#16 ·
More info on the G80 straight from the GM Order/Reference Guide proving there are two different G80 options. Many look up the option codes and assume they mean the same across every model but not always the case.

I get a lot of requests for gear lube info (not just here) and this often comes up with truck owners. Some get misinformed and insist on installing limited slip differential additive in a locking differential. So please excuse me if I get a little abrasive on the subject.

for 2010 GM trucks list of options
G80 Differential, heavy-duty automatic locking rear
GAT All-Terrain Package
GT4 Rear axle, 3.73 ratio
GU4 Rear axle, 3.08 ratio
GU5 Rear axle, 3.23 ratio
GU6 Rear axle, 3.42 ratio

for 2010 Camaro
G80 Differential, limited slip
GM3 Axle, 3.45 ratio
GW6 Axle, 3.27 ratio
JL9 Brakes, 4-wheel antilock, 4-wheel disc

for 2010 Cadillac CTS sedan, sport wagon, CTV-V
G80 Differential, limited slip
J55 Brakes, performance 4-wheel antilock, 4-wheel disc
J56 Brakes, Brembo
J77 Brake, electronic parking
JF5 Pedals, metal
 
#17 ·
So back to the earlier post by 99ChevyZ71:
GU6 AXLE,3.42 RATIO
G80 AXLE,REAR,POSITRACTION,LIMITED SLIP POSITRACTION L/SLIP R/AXL(G80)
This is what he posted after I requested the RPOs off my VIN.

So my truck is a 2004 Sierra 1500 2x4 with the Z85 tow package. Assuming 99Chevy's post to be accurate, that locking G80s in 2004 were not standard on my truck, and that in your last post the G80 RPO offers several types of diffs; I do in fact have the limited slip.

You see, what I've been trying to get my arms around (and what seems to confuse many) is the fact that the term "G80" is just an RPO code. Many (myself included) assign the term G80 as a type of Eaton model for locking differentials. Does this make sense?
 
#18 ·
The G80 does not automatically mean its a Eaton. GM has used Eaton differentials since the 1960's. For instance the differential in my 2002 Trans Am was a G80 but it was made by Torsen. Somewhere I still have the brochure and will look to see if its says G80 and Torsen. I know its says Thorsen in the brochure and I had the factory build sheet that shows G80.

The G80 in my Cadillac is made by Getrag, so no not all G80 are Eaton. In trucks generally speaking yes but who knows what GM might install tomorrow.

I agree, G80 was not standard.

Here is built sheet for the Trans AM, note G80 listed as option, Brochure lists Thorsen as the manf. Also note, car was built on 9-11-2001!

 
#20 ·
WingNut said:
So back to the earlier post by 99ChevyZ71:
GU6 AXLE,3.42 RATIO
G80 AXLE,REAR,POSITRACTION,LIMITED SLIP POSITRACTION L/SLIP R/AXL(G80)
This is what he posted after I requested the RPOs off my VIN.

So my truck is a 2004 Sierra 1500 2x4 with the Z85 tow package. Assuming 99Chevy's post to be accurate, that locking G80s in 2004 were not standard on my truck, and that in your last post the G80 RPO offers several types of diffs; I do in fact have the limited slip.
No, for the Sierra, the G80 means the Eaton locker. No friction additive needed.

Folks who get RPO printouts from http://www.compnine.com get the "limited slip" text and think they don't have a locker.

As Z15 clearly showed, for trucks, G80 means locker. For cars, G80 is a 'traditional' limited slip.

I have one in my 04 Silverado (along with the Z85 tow package).

Part of the confusion is that the Eaton G80 locker also has clutch plates inside but used for a totally different reason to lock the axle. [See the video I posted.]
 
#22 ·
Yes..............

Limited slip axles are performance oriented axles where some slip is needed to gain traction on pavement

Lockers are for traction in off road conditions
 
#23 ·
I located this bulletin

#PIP4054C: Eaton Locking Differential Chatter Shudder Noise on Turns - keywords bind grab grind - (Aug 26, 2008)

Subject: Eaton Locking Differential Chatter Shudder Noise on Turns

Models: 2004-2007 Buick Rainier

2000-2009 Cadillac Escalade, ESV, EXT

2002-2009 Chevrolet Avalanche

2004-2009 Chevrolet Colorado

2003-2009 Chevrolet Express

2000-2009 Chevrolet Suburban, Tahoe

2000-2007 Chevrolet Silverado Classic

2007-2009 Chevrolet Silverado

2002-2009 Chevrolet Trailblazer

2004-2009 GMC Canyon

2002-2009 GMC Envoy

2000-2009 GMC Yukon, Yukon Denali, Yukon XL

2000-2007 GMC Sierra Classic

2007-2009 GMC Sierra

2003-2009 GMC Savana

Equipped With a Locking Rear Differential RPO G80

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Customers may comment on a chatter or shudder from the rear axle on vehicles equipped with an Eaton locking differential. This condition would be noticed in parking lot maneuvers, turning, or during locking differential engagement and may be more noticeable when the differential is hot. Locking differential clutch chatter may be causing this concern.

Note 1: This does not apply to vehicles equipped with RPO QS4 (Quadrasteer) which is part of option package NYS. Quadrasteer vehicles use Dana axles and have a different fluid requirement.

Note 2: This PI does not apply to vehicles equipped with a RPO G86 limited slip differential.

Recommendation/Instructions:
If differential clutch chatter is encountered in a vehicle equipped with an Eaton locking differential, flush, drain and refill the differential with new synthetic fluid, use the fluid part number listed in SI for the vehicle currently being worked on. If the condition returns replace the rear differential clutch plates and refill the differential with new synthetic fluid, use the fluid part number listed in SI for the vehicle currently being worked on. Refer to eSI for clutch plate replacement and set up procedures.

Note 1: Eaton locking differentials used in 10.5" rear axles are equipped with steel clutch plates. It is a design characteristic of these steel clutch plates to exhibit more clutch chatter than other models.

***Important: Installing any friction modifier causes the clutch pack in the locking differential to slip and miss engagement. A fluid flush can often remove debris that is a contributor to clutch chatter. Adding friction modifier additive can cause a loss of locking differential functionality***
 
#24 ·
Vehicle: SIE 1500 EXT CAB STD BOX
Year: 2004

RPO Description
UB1 RADIO AM/FM STEREO, SEEK/SCAN. AUTO REV MUSIC SEARCH CASS, CD, AUTO TONE, DATA SYSTEM, CLOCK, ETR STEREO W/CASSETTE,CD,AUTO TONE(UB1)
UQ3 SPEAKER SYSTEM,PERFORMANCE ENHANCED AUDIO ENHANCED SPKR SYS(UQ3)
VB3 BUMPER,REAR STEP,INCLUDES IMPACT STRIP(CHROME) CHROME STEP BPR(VB3)
VG3 STRIP,FRONT BUMPER IMPACT FRT BPR IMP STR(VG3)
VK3 LICENSE PLATE,FRONT MOUNTING PACKAGE FRT LIC PLT MTG PKG(VK3)
VP6 NOISE LEVEL CONTROL NOISE LVL CONT(VP6)
VR4 TRAILER HITCH(WEIGHT DISTRIBUTING PLATFORM) EQLZR HITCH(VR4)
VXS VEHICLE - COMPLETE
V22 GRILLE,RADIATOR(CHROME) CHROME GRL(V22)
V73 VEHICLE STATEMENT - US/CANADA US/CANADA VEHICLE STATEMENT(V73)
V76 HOOK,FRONT TOW FRT TOW HOOK(V76)
HOOK,FRONT TOW(EXPORT) FRT TOW HOOK(V76)
XCC TIRE FRONT P255/70R16 BW R/PE ST TL ALS TIRE(XCC)
YCC TIRE REAR P255/70R16 BW R/PE ST TL ALS TIRE(YCC)
YD3 AXLE FRONT (BASE EQUIP) FOR SCHEDULING GVW PLATE FRT AXLE(YD3)
YD6 SPRING,REAR(BASE EQUIPMENT) RR SPRING(YD6)
YE9 CONVENIENCE PKG COMFORT & DECOR LEVEL #3 COMFORT & CONVENIENCE PKG #3(YE9)
ZCC TIRE SPARE P255/70R16 BW R/PE ST TL ALS SPARE TIRE(ZCC)
ZY1 COLOR COMBINATION SOLID SOLID PAINT COMBO(ZY1)
Z82 TRAILERING PACKAGE(SPECIAL)(REESE TYPE HITCH) PROVISION FOR HD TRAILER EQUIP(Z82)
Z85 CHASSIS PACKAGE,INCREASED CAPACITY CHAS PKG(Z85)
Z88 GMC TRUCK G M C(Z88)
1SC PACKAGE-OPTION 03 (1SC)
1SZ PACKAGE OPTION- (1SZ)
59U EXTERIOR COLOR,PRIMARY (59U)
EXTERIOR COLOR,PRIMARY,FINE SILVER BIRCH MET (59U)
6MT COMPONENT FRT LH COMPUTER SEL SUSP (6MT) SUSP(6MT)
69D TRIM COMBINATION CLOTH,VERY DARK PEWTER (69D)
69I INTERIOR TRIM COLOR,VERY DARK PEWTER (69I)
7MT COMPONENT FRT RH COMPUTER SEL SUSP (7MT) SUSP(7MT)
AE7 SEAT,FRT SPLIT,EASY ENTRY EASY ENTRY SPLIT F/SEAT(AE7)
AJ1 GLASS,DEEP TINT(REAR SIDE WINDOWS AND REAR DOOR WINDOW) DEEP TINTED GLS(AJ1)
AL0 SENSOR INDICATOR INFLATABLE RESTRAINT, FRT PASS/CHILD PRESENCE DETECTOR FRT PASS/CHILD PRESENCE DETECTOR INFL REST IND SENSOR(AL0)
AM7 SEAT,REAR FOLDING RR FLDG ST(AM7)
AU0 LOCK CONTROL,REMOTE ENTRY(KEYLESS ENTRY SYSTEM) REMOTE ENTRY LK CONT(AU0)
AU3 LOCK,SIDE DOOR,ELECTRIC ELEC S/D LK(AU3)
A31 WINDOW,ELECTRIC OPERATED,SIDE ELEC SI WDO(A31)
WINDOW,POWER OPERATED,ALL DOORS PWR WINDOWS(A31)
B30 CARPET,FLOOR AND WHEELHOUSE FLR CPT(B30)
B32 COVERING,FLOOR MATS,FRONT AUXILIARY FRT AUX FLR MATS(B32)
B33 COVERING,FLOOR MATS,REAR AUXILIARY RR AUX FLR MATS(B33)
B85 ORNAMENTATION,EXTERIOR,BELT REVEAL MOLDING BELT RVL MLDG(B85)
CJ3 AIR CONDITIONER,FRONT,MANUAL TEMPERATURE CONTROL,AUXILIARY TEMPERATURE CONTROL A/C FRT MAN/AUX CONTROL(CJ3)
C49 DEFOGGER,REAR WINDOW,ELECTRIC ELEC RR WDO DEFG(C49)
DF5 MIRROR,INSIDE,REARVIEW,LT SENSITIVE,COMPASS,O/S TEMP DISPLAY I/S REARVIEW MIR W/COMPASS(DF5)
DK7 CONSOLE ROOF INTERIOR,CUSTOM,COMPASS & OUTSIDE TEMP RF CNSL(DK7)
DL8 MIRROR,OUTSIDE,RH AND LH REMOTE CONTROL,ELECTRIC,DEFOG ELEC R/CON HTD O/S MIR(DL8)
EVA TEST DVT, EVAP EMISSION REQUIREMENT EVAP EMISSIONS REQUIRED(EVA)
E63 BODY EQUIPMENT,FLEETSIDE PICKUP BOX FLEETSIDE PUBX(E63)
FE9 FEDERAL EMISSION CERTIFICATION FED EMIS(FE9)
FWI PLANT CODE FORT WAYNE, IN GM T&B FORT WAYNE,IN PLANT(FWI)
GU6 AXLE,REAR,3.42 RATIO 3.42R(GU6)
G80 AXLE,REAR,POSITRACTION,LIMITED SLIP POSITRACTION L/SLIP R/AXL(G80)
JC3 BRAKE VAC POWER, DISC/DISC, 6,400 LBS 6400# VAC PWR BRAKES(JC3)
KNP COOLING SYSTEM,TRANSMISSION,HEAVY DUTY HVY DUTY TRANS CLG SYS(KNP)
KUP THROTTLE CONTROL VARIABLE SPEED (ELECTRONIC) ELECTRONIC THROTTLE CONTROL(KUP)
K34 CRUISE CONTROL,AUTOMATIC,ELECTRONIC CRCONT(K34)
K47 AIR CLEANER HIGH CAPACITY HI CAPACITY A/CL(K47)
K68 GENERATOR,105 AMPERE 105 AMP(K68)
LM7 ENGINE GAS, 8 CYL, 5.3L, MFI 5.3T(LM7)
M30 TRANSMISSION,AUTOMATIC 4 SPEED,4L60E,ELECTRONIC 4-SPD A/TRANS(M30)
NP5 STEERING WHEEL,LEATHER WRAPPED LEATHER WRAPPED STRG WHL(NP5)
NT8 EMISSION SYSTEM FEDERAL, TIER 2 A TIER 2 A FED EMIS(NT8)
PDJ CONTROL - SALES ITEM NO. 127
PDU CONTROL - SALES ITEM NO. 137
PF4 WHEEL,16X7(ALUMINUM) AL WHL(PF4)
QCC TIRE ALL P255/70R16 BW R/PE ST TL ALS TIRE(QCC)
Q4B GVW RATING 6200 LBS 6200 GVWR(Q4B)
R6I CONTROL - SALES ITEM NO. 09
R9U CONTROL - SALES ITEM NO. 95
SAF LOCK SPARE TIRE, HOIST SHAFT SPARE TIRE LOCK HOIST SHF(SAF)
SLM SALES PROCESSING - STOCK ORDERS
TFE SALES INCENTIVE - COMMITMENT PLUS
T96 LAMP,FRONT FOG FRT FOG LP(T96)
 
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