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How Do I Know My Truck Has A Locking Diff?


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#1 oneillt

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Posted 16 March 2011 - 11:27 PM

Hey guys, quick question.
New truck is an 04' GMC z71, and I heard that some z71's can come through the line without the locking diff. I heard the RPO code for the locking diff is g80, but then I also read in a post that it is possible to have this code and not have the locker because it is the same code for a limited slip axle? I ran my vin into the rpo code/rarity site and it spit this back at me
"G80AXLE,REAR,POSITRACTION,LIMITED SLIP POSITRACTION L/SLIP R/AXL(G80)"
Does this mean I do not have the locker, and just have regular limited slip?

*edit* I know i can just go find an icy patch to figure this out, but I'm not gunna have the truck for another week.

Edited by oneillt, 16 March 2011 - 11:29 PM.


#2 pm26

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Posted 16 March 2011 - 11:41 PM

If you have a limited slip differential instead of the locking type, both wheels will rotate in the same direction if you jack up the truck by the rear differential and spin one rear wheel by hand (vehicle in neutral). If you have a locking differential, the wheels will rotate in opposite directions, as this differential acts as an open differential when not locked.

#3 RyanbabZ71

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Posted 17 March 2011 - 05:06 AM

If it has limited slip it is not a factory option. The only factory option is the G80 locking rear differential

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#4 elcamino

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Posted 17 March 2011 - 05:33 AM

They do not put limited slip axles in trucks

A G80 in a truck is a Eaton locker.

In 2004 G80 was not standard equipment, if you wanted it you had to pay extra to get it and it was not part of the Z71 option. Later models GM did package with the option but not in 2004.

If you have G80, it will show on the label in the glove box along with all the options on the truck. If G80 is not there, you got the standard open differential.

People get confused because they assume an option description is the same across all models and that is often not the case. G80 means something different depending on the vehicle it is installed in.

G80 - G80AXLE,REAR,POSITRACTION,LIMITED SLIP POSITRACTION L/SLIP R/AXL(G80) is the description for only in cars

G80 Differential, heavy-duty automatic locking rear is the description for trucks

here is a official list of GM options from the GM car lines. Notice what they call G80 for each..

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

As you can see from the lists, a limited slip axle is a performance axle which serves little use in a truck

Folks who get RPO printouts from online lookups get the "limited slip" text and think they don't have a locker. Those are programed wrong...

I wonder how many CTV-V and Camaro owners think they have a locker because they are looking at an option list for trucks?

Edited by elcamino, 17 March 2011 - 05:58 AM.

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#5 snakedoctor

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Posted 17 March 2011 - 09:06 AM

The only truck to get a limited slip was the Quadrasteer and it was a G86. The G80 in a truck as has been said will be a locking diff.

Now. Starting in 2004 The Z71 INCLUDED the G80 locking diff. It was not a part of the Z71 but a part of the off road package required by the Z71. Before 2004 it was a stand alone option.

It would be listed like this in the dealer RPO code book..

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#6 09LowesSilverado

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Posted 17 March 2011 - 09:59 AM

Hey guys, quick question.
New truck is an 04' GMC z71, and I heard that some z71's can come through the line without the locking diff. I heard the RPO code for the locking diff is g80, but then I also read in a post that it is possible to have this code and not have the locker because it is the same code for a limited slip axle? I ran my vin into the rpo code/rarity site and it spit this back at me
"G80AXLE,REAR,POSITRACTION,LIMITED SLIP POSITRACTION L/SLIP R/AXL(G80)"
Does this mean I do not have the locker, and just have regular limited slip?

*edit* I know i can just go find an icy patch to figure this out, but I'm not gunna have the truck for another week.


Just check your Glove Box RPO List, and if one of the Codes reads G80, then Congratulations, You have an Eaton Locking Rear Differential!

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#7 gates59

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Posted 17 March 2011 - 10:42 AM

If you have the vin number go here and check.
http://www.compnine.com/vid.php

#8 elcamino

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Posted 17 March 2011 - 11:07 AM

If you have the vin number go here and check.
http://www.compnine.com/vid.php

This is where people get the idea they have a limited slip differential. I have seen it come back as limited slip so this site in not reliable. Matter of fact is shows my CTS as a DTS so there are bugs in that lookup. It also comes back with the wrong paint color.

A while back I had one fella come in the shop for gear lube and wanted an additive for his limited slip. When I told him the truck did not have a limited slip he pulled out print-out from this online site or another just like it that said he had a Limited Slip Differential, not a locker. It was wrong! If it tells you your truck has a G80 limited slip its lying to you.

Edited by elcamino, 17 March 2011 - 11:17 AM.

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#9 SparkySparks

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Posted 17 March 2011 - 01:33 PM

If you have the vin number go here and check.
http://www.compnine.com/vid.php

This is where people get the idea they have a limited slip differential. I have seen it come back as limited slip so this site in not reliable. Matter of fact is shows my CTS as a DTS so there are bugs in that lookup. It also comes back with the wrong paint color.

A while back I had one fella come in the shop for gear lube and wanted an additive for his limited slip. When I told him the truck did not have a limited slip he pulled out print-out from this online site or another just like it that said he had a Limited Slip Differential, not a locker. It was wrong! If it tells you your truck has a G80 limited slip its lying to you.



That site also has my truck listed as being a White truck.

#10 gates59

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Posted 17 March 2011 - 01:46 PM

I'm sorry I was just trying to help.

#11 SparkySparks

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Posted 17 March 2011 - 02:41 PM

I'm sorry I was just trying to help.


Didn't mean it was bad, just take what ever it says with a grain of salt. I got the dealer to print out a build sheet for me because I was trying to figure out why the website listed my truck as being white. I wanted to make sure something hadn't gotten mixed up.

#12 G-Street

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Posted 17 March 2011 - 05:12 PM

Easiest way to get info on your rear end is to look in your glovebox on the sticker on the 'door' (for lack of a better word). If in those tiny little letters it reads G80 you have a G80. If not, you do not.

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