12 bolt rear end identification searched everywhere!!

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Ryc10

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Code on passenger side axle reads HA0426



Other codes Nf3896838
Gm56
any help I’ve searched all the charts and no luck

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Ryc10

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Sorry just noticed posted it under wrong category don’t know how to change it
 

bucket

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Moved it for ya.

I'm no help with the numbers, but I wouldn't be afraid to pull the cover for an inspection. That will tell you exactly what you have and you can put fresh fluid in.
 

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From what I remember the stamping on the axle tubes has nothing to do with the carrier or R&P. I can't recall all the numerical data on it but it just comes down to a production serial date. The internals would have been on the tag in the glove box with a metal tag on the lower bolt on the diff cover but a lot of people took them off during a service and for some reason never thought it was important to put them back on.
 

fast68chevy

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well you remember wrong.,. the prefix letters stamping has everythign to do with the ratio, and whats what these letters stampings are for exactly... most GM truck axles werent tagged like many of the dana and ford axles were. a tag on the fill plug on the posi/lim slip equipped axles was about the only time you saw a tag on the 12 bolts.. otherwise no tag on these axles.

the HA prefix stamp code is for the ratio

HB,LL,RA.TR,TT,TU are 3.07s

HA,HJ,HQ,MF,TQ,MI,MK are 3.73s

HK,HL,HR,ME,MG,TS are 4.11s

HC,HN,MU are 3.73 Posi

HO,HP,JQ, are 4.11 Posi


the four numbers are the julian date.

0426 is the 42nd day of 1976


call local dealer parts counter with that code and year make model and they can tell you what it was from factory... if its the original axle anyways.. it was a 1976 3.73 open carrier

and in these 12 bolt truck axles you would rather have open diff than the G80 gov lok, AKA grenade-lok
 
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HotRodPC

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HotRodPC

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I'm wondering if this 12 bolt is even a truck 12 bolt. Is this installed in your truck now?
 

dvdswan

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Best way to find out the type of rear end is usually the shape of the cover...

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as for the gears, the best way is to pop the cover and read the stamp on the ring gear...

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while its open you can identify what type of carrier you have as well.
 

Ryc10

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Yes
 

Ryc10

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Yes it’s in the truck now. The motor in the truck was a 305 out of a 76 Camaro but the rear end is def a truck 12b

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AuroraGirl

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well you remember wrong.,. the prefix letters stamping has everythign to do with the ratio, and whats what these letters stampings are for exactly... most GM truck axles werent tagged like many of the dana and ford axles were. a tag on the fill plug on the posi/lim slip equipped axles was about the only time you saw a tag on the 12 bolts.. otherwise no tag on these axles.

the HA prefix stamp code is for the ratio

HB,LL,RA.TR,TT,TU are 3.07s

HA,HJ,HQ,MF,TQ,MI,MK are 3.73s

HK,HL,HR,ME,MG,TS are 4.11s

HC,HN,MU are 3.73 Posi

HO,HP,JQ, are 4.11 Posi


the four numbers are the julian date.

0426 is the 42nd day of 1976


call local dealer parts counter with that code and year make model and they can tell you what it was from factory... if its the original axle anyways.. it was a 1976 3.73 open carrier

and in these 12 bolt truck axles you would rather have open diff than the G80 gov lok, AKA grenade-lok
Wdym? I have a 79 stepside 1/2 frame that was made into a truck bed trailer. At least I think its a 79. But it has a 12 bolt with G80 on the cover :O
 

AuroraGirl

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That would be a 12 bolt right?
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It says G80 on the cover
 

HotRodPC

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That would be a 12 bolt right?
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It says G80 on the cover
Someone must have put the G80 on the cover. Is it hand written or engraved? The factory doesn't mark them generally.
 

AuroraGirl

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it says GM80 in the stamped portion to the right of the center
 

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