Rearend I.D. question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

littlebubba · 09-27-2002, 11:11 AM

Can anybody tell me what codes to look and where to for on a 73-81 truck to tell if it has a " POSI " rearend without having to pull the cover and look? Would the codes or info be on the glovebox door? Do they attach a tag to them that says limited slip fluid only or anything like that, if it all ready out of the truck? I have been told there is a code stamped on the axle housing, true or false? I am trying to find a 12 bolt limited slip or posi for my 2WD 81 BLAZER.

HPD-CA · 10-02-2002, 09:47 AM

The RPO codes paper use to be placed under the front seat, between the springs and foam. You are right on the glove box list. Try this link for axle info. I found it very helpful.

http://coloradok5.com/axleguide.shtml

Dean....

hrc200x · 10-02-2002, 03:13 PM

I have a 80 1 ton 4x4 and the sticker in the glove comparment said something like locking rear end. I've also seen that same sticker stuck in the engine bay on the driver side inner fender.

**crossy** · 10-05-2002, 12:00 AM

Just a little info. yes there were option codes in the glove box and sometimes on the inner fender but they are seldom still there in the salvage yard. the code for posi has always been, G80, .
there are codes stamped onto the rear on the passenger axle tube at around dead top to 90 degree front. take a file & flashlight with you ,it works well ,I have most of the codes for 73-87.
75% of all 78-80's have 2.73 ratio that i found. 75-77 had a lot of 3.40 ratio and 73-74's used 3.73 & 3.40. forget any 10 bolts they used them as early as 78. DAVE

littlebubba · 10-05-2002, 01:30 AM

I have an 1981 12 -bolt "open rear" that i want to change gears to 3:40ish or 3:73 and put in posi or limited slip while i am at it. And don't want to take the cover off every rear to inspect, unless its all ready out of the truck. I have been told to look for a Suburban with trailing package or pickup with same, but need the codes or at least some clues.

**crossy** · 10-05-2002, 10:20 AM

sorry guy but there are literally HUNDREDS of codes because they changed ALMOST every year. I hear your plight though, been there before. if you just HAVE to find a used posi then jack it up and spin the wheels , opposite directions are open , same direction are posis. go write down all the codes you can find one day and come to herre to find out what they are.DAVE

**crossy** · 10-08-2002, 11:23 PM

BTW. I do have a 12 bolt posi unit and a set of 3.40 gears here somewhere for a 12 bolt. DAVE

littlebubba · 10-09-2002, 01:28 AM

Which type posi unit is that you have for sale? Condition and how much? Same for the gears; that ratio will work out ok, best of both worlds, I guess.

09-27-2002, 11:11 AM	#1
littlebubba Registered User Join Date: Jun 2002 Location: Clinton Twp., Michigan Posts: 323	Rearend I.D. question Can anybody tell me what codes to look and where to for on a 73-81 truck to tell if it has a " POSI " rearend without having to pull the cover and look? Would the codes or info be on the glovebox door? Do they attach a tag to them that says limited slip fluid only or anything like that, if it all ready out of the truck? I have been told there is a code stamped on the axle housing, true or false? I am trying to find a 12 bolt limited slip or posi for my 2WD 81 BLAZER.

10-02-2002, 09:47 AM	#2
HPD-CA Registered User Join Date: Sep 2002 Location: Northern CA Posts: 20	Axle ID'er The RPO codes paper use to be placed under the front seat, between the springs and foam. You are right on the glove box list. Try this link for axle info. I found it very helpful. http://coloradok5.com/axleguide.shtml Dean.... __________________ "In science there is only physics; everything else is stamp collecting." --Ernest Rutherford---

10-02-2002, 03:13 PM	#3
hrc200x Registered User Join Date: Sep 2002 Location: Minnesota Posts: 201	I have a 80 1 ton 4x4 and the sticker in the glove comparment said something like locking rear end. I've also seen that same sticker stuck in the engine bay on the driver side inner fender. __________________ '75 Chevy 3/4 4x4, 6" suspension lift, 3" body lift, 3" lifted gas tanks, '83 cab, '88 clip, 35" cooper tires, American Racing Baja rims, 350, 700r4, 208.

10-05-2002, 12:00 AM	#4
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	rear codes & ID Just a little info. yes there were option codes in the glove box and sometimes on the inner fender but they are seldom still there in the salvage yard. the code for posi has always been, G80, . there are codes stamped onto the rear on the passenger axle tube at around dead top to 90 degree front. take a file & flashlight with you ,it works well ,I have most of the codes for 73-87. 75% of all 78-80's have 2.73 ratio that i found. 75-77 had a lot of 3.40 ratio and 73-74's used 3.73 & 3.40. forget any 10 bolts they used them as early as 78. DAVE __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

10-05-2002, 01:30 AM	#5
littlebubba Registered User Join Date: Jun 2002 Location: Clinton Twp., Michigan Posts: 323	Need posi I have an 1981 12 -bolt "open rear" that i want to change gears to 3:40ish or 3:73 and put in posi or limited slip while i am at it. And don't want to take the cover off every rear to inspect, unless its all ready out of the truck. I have been told to look for a Suburban with trailing package or pickup with same, but need the codes or at least some clues.

10-05-2002, 10:20 AM	#6
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	codes sorry guy but there are literally HUNDREDS of codes because they changed ALMOST every year. I hear your plight though, been there before. if you just HAVE to find a used posi then jack it up and spin the wheels , opposite directions are open , same direction are posis. go write down all the codes you can find one day and come to herre to find out what they are.DAVE __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

10-08-2002, 11:23 PM	#7
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	BTW rears BTW. I do have a 12 bolt posi unit and a set of 3.40 gears here somewhere for a 12 bolt. DAVE __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

10-09-2002, 01:28 AM	#8
littlebubba Registered User Join Date: Jun 2002 Location: Clinton Twp., Michigan Posts: 323	Which posi is that? Gears? Which type posi unit is that you have for sale? Condition and how much? Same for the gears; that ratio will work out ok, best of both worlds, I guess.



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