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Decoding Help - 12 Bolt

4K views 25 replies 6 participants last post by  bcm66 
#1 ·
Can you guys help me decode this 12 Bolt out of my 69? It came with the car, 3.73 non-posi. I'm only able to pull axle stamp numbers.

The casting numbers are almost unreadable, there is so much paint caked over it. I will have to scrub them.

Also, I was unable to locate casting #'s, I looked on CRG, is the number on top or bottom of the area that they've called out? I don't see the numbers anywhere near. It's a tight squeeze under there!

The axle stamp looks like 0 ?Z 05120 E

Also, the rear end has traction bars, is this original to the axel?

Thanks.
 

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#7 ·
You are correct in saying those were not installed by the factory on a first generation Camaro. That doesn't mean that someone else didn't add those to a first generation Camaro. The rear could still be factory stock rear in a first gen !
 
#4 · (Edited)
Joe, Both the slapper bars and the sway bar are added to a first gen. axle.

C QZ 0512G
.........E

A QZ code in '69 was for a 4.56 12 Bolt. (If that is a Q)

late 69 axles may be stamped with the 1970 style C prefix (e.g. CBT instead of just BT)

The E - stands for an Eaton Posi.

I don't think it IS what it WAS.
 
#8 ·
Nothing on the rear points to a '66 Chevelle. At least I don't think it does.

The 3 letter code points to a late '69 Camaro rear.

C QZ = 4.56 gearing; 0512 = May 12; G = Detroit Gear & Axle plant

E = Eaton Posi

The posi carrier and gears could have easily been changed to more "street friendly" 3.73 gears. They would of had to change the carrier to swap to a different series of gears. I don't think 3.73's were available in a 4 series in the early 1970's.

The only thing that confuses me is that it supposedly came with 4 wheel Disc brakes !
 
#11 ·
You are correct, it does look more like the one on Nastyz28. I'll do some more digging.
 
#14 · (Edited)
COZ is a 1970 Camaro code.

Assembly date on there of May 12 points to it being a 70, but get the casting number and casting date off the center section. Might need some paint remover. In 1970, in a Camaro rear axle coded COZ is for 3.73 locking (posi).

Posi may have given out and someone stuck an open carrier in there. What are the numbers on the ring gear? If you have the cover off.
 
#16 ·
Hm, I didn't see the COZ code on CRG. I didn't keep the old ring gear, or did you mean the numbers on the pumpkin? The rear end was a mess when we pulled the gears, lots of metal shavings inside the housing. Servicing the rear end was above my paygrade, so my buddy's shop replace the gears, posi, bearings etc. He said it took him an hour to clean it out from all the metal in there.



COZ is a late 69 and 70 code for Camaros.

Assembly date on there of May 12 points to it being a 70, but get the casting number and casting date off the center section. Might need some paint remover. In 1970, in a Camaro rear axle coded COZ is for 3.73 locking (posi).

Posi may have given out and someone stuck an open carrier in there. What are the numbers on the ring gear? If you have the cover off.
 
#15 ·
It's probably a '70 because the original spring perches have been cut off and after market perches have been welded on. The '70 rear end is 1/2 inch wider on each side for a total of 1 inch. The spring perches are also about 2 1/4 inches farther apart, which would explain why the after market perches were used.
 
#17 ·
That letter actually looks like a "sideways" G .
 
#26 ·
Well sort of...

G1 means Detroit Gear & Axle plant, first shift.

It appears the C0Z (C zero letter) stamps are first shift only - based on the limited examples for 70 Camaro 12 bolts shown in the thread you posted. Just means that the person doing the stamping on that shift used a zero instead of the letter O.
 
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