12 bolt from hades - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 42 (permalink) Old May 14th, 19, 9:11 PM Thread Starter
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Beth
 
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12 bolt from hades

Recently bought a super nice 67 Chevelle with a modified 12 bolt rear.

The brackets are a mystery, not sure exactly what was done. Hope somebody can tell.

The lower control arm bracket is supposed to be about an inch from the backing plate and now it is about 3".

The shock mount may be original ?

And the coil spring support has been replaced by a redneck attempt at fabrication - it's horrible.

I am about to cut these brackets off and grind them smooth so someone can weld on a set of brackets from Currie.

It sure would be nice if the shock mounts could stay where they are ?
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67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #2 of 42 (permalink) Old May 14th, 19, 9:44 PM
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Ole
 
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Re: 12 bolt from hades

The factory shock and control arm mounting bracket is actually a single bracket that wraps around the axle tube, while combining both functions. The coil spring mount is separate. I recently purchased a rather rare 12-bolt housing where some genius had very crudely attempted to relocate the shock/control arm mounts. Given I wanted to retain a factory configuration, I had a professional welder friend remove the butchered shock/control arm brackets from the 12 bolt I had purchased, then cut a serviceable pair of shock/control arm brackets from a spare 10-bolt rear axle I had laying around, and using another complete rear end as a measuring template, weld the 10 bolt brackets to the 12 bolt I had purchased.

The only problem with using aftermarket brackets is that the shock and control arm brackets are 2 separate pieces, not a single piece as the GM brackets are designed to be. But if not concerned with originality, I would use the aftermarket brackets.

But before you cut anything, on second look, I would compare this rear axle with a known factory set up, as the shock/control arm brackets look to be unmolested and in the right place to me. I could be wrong, but I do not think so. You will most definitely need new spring mounts. Those are pretty comical. Use the late year '67 and newer "top hat" design, which is superior to the early version.
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post #3 of 42 (permalink) Old May 14th, 19, 10:28 PM Thread Starter
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Re: 12 bolt from hades

Quote:
Originally Posted by Saltherring View Post
The factory shock and control arm mounting bracket is actually a single bracket that wraps around the axle tube, while combining both functions. The coil spring mount is separate. I recently purchased a rather rare 12-bolt housing where some genius had very crudely attempted to relocate the shock/control arm mounts. Given I wanted to retain a factory configuration, I had a professional welder friend remove the butchered shock/control arm brackets from the 12 bolt I had purchased, then cut a serviceable pair of shock/control arm brackets from a spare 10-bolt rear axle I had laying around, and using another complete rear end as a measuring template, weld the 10 bolt brackets to the 12 bolt I had purchased.

The only problem with using aftermarket brackets is that the shock and control arm brackets are 2 separate pieces, not a single piece as the GM brackets are designed to be. But if not concerned with originality, I would use the aftermarket brackets.

But before you cut anything, on second look, I would compare this rear axle with a known factory set up, as the shock/control arm brackets look to be unmolested and in the right place to me. I could be wrong, but I do not think so. You will most definitely need new spring mounts. Those are pretty comical. Use the late year '67 and newer "top hat" design, which is superior to the early version.
Thanks, I just measured it from axle flange-to-axle flange and it's 55.25".

This is a 68-72 12 bolt. Ugh, oh well. I will sell this and either go with a Moser or find a rebuildable 66-67 rear.

It had a 2.56 gears in it so that's useless LOL

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #4 of 42 (permalink) Old May 14th, 19, 10:34 PM
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Ole
 
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Re: 12 bolt from hades

Given the rarity of your car you probably will be looking for a '67 axle assy dated closely to your car. A '67 rear may cost a bit more than a '68-'72. Good luck.
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post #5 of 42 (permalink) Old May 14th, 19, 10:50 PM Thread Starter
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Re: 12 bolt from hades

Quote:
Originally Posted by Saltherring View Post
Given the rarity of your car you probably will be looking for a '67 axle assy dated closely to your car. A '67 rear may cost a bit more than a '68-'72. Good luck.
There's a guy 1 hour south of me that has a rust-bucket 67SS for sale.

He says he will sell the rearend seperately but I've seen this ad for months.

Who knows, maybe he is ready to sell ?

I'm building this car to be somewhat bullet-proof, so a Moser will go in if I can't find one at a reasonable price.

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #6 of 42 (permalink) Old May 15th, 19, 1:35 AM
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Re: 12 bolt from hades

65-66 12 bolts in TN if you want the narrow
https://www.chevelles.com/forums/358...olt-rears.html

Or
Contact Tory aka Lionel-n-Chevelles
https://www.chevelles.com/forums/mem...chevelles.html

Chevelle Malibu ss 64
489 BB with parts from Lewis racing
Alumitech radiator with dual spals
Th 400 Edge 9.5" converter
57 3/4” wide 12 bolt: Eaton posi, Us gear 3.31, Toms KA 33 splines axles
Malibu ss 64 is online now  
post #7 of 42 (permalink) Old May 15th, 19, 2:32 PM Thread Starter
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Beth
 
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Re: 12 bolt from hades

Quote:
Originally Posted by Malibu ss 64 View Post
65-66 12 bolts in TN if you want the narrow
https://www.chevelles.com/forums/358...olt-rears.html

Or
Contact Tory aka Lionel-n-Chevelles
https://www.chevelles.com/forums/mem...chevelles.html
Thanks Marcus !
Malibu ss 64 likes this.

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #8 of 42 (permalink) Old May 15th, 19, 2:38 PM Thread Starter
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Beth
 
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Re: 12 bolt from hades

Quote:
Originally Posted by Saltherring View Post
Given the rarity of your car you probably will be looking for a '67 axle assy dated closely to your car. A '67 rear may cost a bit more than a '68-'72. Good luck.
I looked in a 300 mile radius around Nashville TN on Craigslist with no luck. So if anyone sees a 67 12 bolt for sale, let me know !

Thanks

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #9 of 42 (permalink) Old May 15th, 19, 7:57 PM
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post #10 of 42 (permalink) Old May 15th, 19, 9:25 PM
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Re: 12 bolt from hades

Whats the size diff? could it not be made up with offset wheels?

"A Nation of Sheep will beget a Government of Wolves." Edward R. Murrow
“The last official act of any government is to loot the treasury.” – George Washington
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post #11 of 42 (permalink) Old May 15th, 19, 10:07 PM Thread Starter
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Re: 12 bolt from hades

He's already sold his 12 bolt. But please keep looking guys !
--------------
2cool : Whats the size diff? could it not be made up with offset wheels?

The 67 is 2" narrower and I already have my wheels. It's kind of a rare car so I want to keep as much original as possible (to the eye).
-----------

The 12 bolt I have has a casting number : 3959038

So it came from a 1969 and 1970 model year Chevelle or Monte Carlo ?

The date code was hard to read but looks like "B289" for Feb 28, 1969 ?

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #12 of 42 (permalink) Old May 15th, 19, 10:37 PM Thread Starter
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Beth
 
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Re: 12 bolt from hades

Quote:
Originally Posted by Saltherring View Post
The factory shock and control arm mounting bracket is actually a single bracket that wraps around the axle tube, while combining both functions. The coil spring mount is separate. I recently purchased a rather rare 12-bolt housing where some genius had very crudely attempted to relocate the shock/control arm mounts. Given I wanted to retain a factory configuration, I had a professional welder friend remove the butchered shock/control arm brackets from the 12 bolt I had purchased, then cut a serviceable pair of shock/control arm brackets from a spare 10-bolt rear axle I had laying around, and using another complete rear end as a measuring template, weld the 10 bolt brackets to the 12 bolt I had purchased.

The only problem with using aftermarket brackets is that the shock and control arm brackets are 2 separate pieces, not a single piece as the GM brackets are designed to be. But if not concerned with originality, I would use the aftermarket brackets.

But before you cut anything, on second look, I would compare this rear axle with a known factory set up, as the shock/control arm brackets look to be unmolested and in the right place to me. I could be wrong, but I do not think so. You will most definitely need new spring mounts. Those are pretty comical. Use the late year '67 and newer "top hat" design, which is superior to the early version.
Thanks for the help.
I just ordered two of the coil spring supports from Currie :

https://www.currieenterprises.com/CE-7011-DC

I'll clean up this rear end housing and sell it to recover what I can for the 67 housing.

If I narrow this 69 housing, will the brackets still work ? Or will they not line up correctly in a 67 ?

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
nashville beth is offline  
post #13 of 42 (permalink) Old May 15th, 19, 10:44 PM
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Re: 12 bolt from hades

Well if all else fails and you don't want to spend 2+ grand or more for a special built unit you can always have the ends cut off shortened and buy new axles to fit.
I seem to recall that needs to be done to install rear disc brakes but I may be wrong about that.

"A Nation of Sheep will beget a Government of Wolves." Edward R. Murrow
“The last official act of any government is to loot the treasury.” – George Washington
http://s146.photobucket.com/albums/r241/gregs_photo/
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post #14 of 42 (permalink) Old May 16th, 19, 6:31 AM
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Re: 12 bolt from hades

Quote:
Originally Posted by nashville beth View Post
He's already sold his 12 bolt. But please keep looking guys !
--------------
2cool : Whats the size diff? could it not be made up with offset wheels?

The 67 is 2" narrower and I already have my wheels. It's kind of a rare car so I want to keep as much original as possible (to the eye).
-----------

The 12 bolt I have has a casting number : 3959038

So it came from a 1969 and 1970 model year Chevelle or Monte Carlo ?

The date code was hard to read but looks like "B289" for Feb 28, 1969 ?
Th difference is only 1”, looks like it needs a total rebuild if you have a reputable shop around let them shorten it and go with ”ford style” ends.

Chevelle Malibu ss 64
489 BB with parts from Lewis racing
Alumitech radiator with dual spals
Th 400 Edge 9.5" converter
57 3/4” wide 12 bolt: Eaton posi, Us gear 3.31, Toms KA 33 splines axles
Malibu ss 64 is online now  
post #15 of 42 (permalink) Old May 16th, 19, 6:34 AM
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Marcus
 
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Re: 12 bolt from hades

Quote:
Originally Posted by nashville beth View Post
Thanks for the help.
I just ordered two of the coil spring supports from Currie :

https://www.currieenterprises.com/CE-7011-DC

I'll clean up this rear end housing and sell it to recover what I can for the 67 housing.

If I narrow this 69 housing, will the brackets still work ? Or will they not line up correctly in a 67 ?
Yes the brackets will line up if in oem location the difference is outside the brackets.

Chevelle Malibu ss 64
489 BB with parts from Lewis racing
Alumitech radiator with dual spals
Th 400 Edge 9.5" converter
57 3/4” wide 12 bolt: Eaton posi, Us gear 3.31, Toms KA 33 splines axles
Malibu ss 64 is online now  
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