12 bolt rear end question

[shipma3]

kay i just got a 12 bolt truck rear end out of a 1980 chevy k10, but it says it had the gt4 option on the rear end what does this mean?

[b454rat]

1980 would be a 10 bolt I think. But anyways GT4 is 3.73

[Captainfab]

I agree. The original rear differential in a 1980 K10 should be a 8.5" 10 bolt. The last year for the 12 bolt in the K series was '79. In the C series trucks they were available thru '82.

[shipma3]

weird this one is a 12 bolt out of an 1980 k10 lol i counted the bolts on the diff cover and it is a 12 bolt so i assume a 1980 12 bolt is pretty rare then and the vin on the receipt for the part does match for a 1980

[crazy longhorn]

Through 1982 on the 12 bolt....some apps may have been 10 bolt, but 82 was the last yr on the 12 bolt ? My sources show me this, & yes it is a 3.73 gear.....but is it a "gov bomb" , or a good eaton clutch posi? Shoot a pic , if you can crazyL

[Captainfab]

It could quite possibly be an early production 1980.

I don't have my RPO code list here, to look up what GT4 says, but I do know that the RPO code for a Gov-Lock is G80

[b454rat]

I know GT4 is 3.73, GT5 is 4.10, GU6 is 3.42, I can go on!!!!! G80 is the code for locking diff, but anything late 70s and up won't have the clutch type posi. Only G and I think they are B bodies (Caprice, Impala LeSabre) will have clutch type posi. I look all the time in junkyards for rears and posi's and such, scary, I even know some Ferd stuff.....But just do a google for RPO codes, probly half million of them out there...

[shipma2]

it's not a posi lol it's a average run of the mill 12 bolt from the wrecking yard pulled from underneath a 1980 k10. the receipt i got from the wrecker gave me the vin number and i checked it and it conformed to a 1980 k10

[motornut]

my 79 Jimmy has RPO 1HE4 is a G80 and it's 3.4