12 bolt from hades - Page 2 - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #16 of 42 (permalink) Old May 16th, 19, 8:11 AM
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Greg.
 
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Re: 12 bolt from hades

Beth if I lived closer you could have my old 67 12 Bolt

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67 Chevelle Malibu SS Cdn
Born 283 / PG / A51
468/TH400 2,500 stall/ S60 3.70 Gs
Prev Best on M/T ET S/S #3454 street Tires/Dress 2018/05/20
60' = 1.664
1/8 = 7.532 et / 91 mph
1/4 = 11.814 et / 115 mph
NEW Best with 3,500+ Stall TC 2019/06/23
60' = 1.561
1/8 = 7.411 et / 90.18 mph
1/4 = ??.??? et / ??? mph


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post #17 of 42 (permalink) Old May 16th, 19, 12:18 PM
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Re: 12 bolt from hades

I was thinking the shock mounts were in he wrong place at least compared to my 69, look a the 67 above then look at Beth's pics.

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post #18 of 42 (permalink) Old May 16th, 19, 12:25 PM
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Re: 12 bolt from hades

Casting numbers found to be the most prevalent in Chevelle 12-bolt rear ends:

1965 Chevelle 3859140N
1966 Chevelle 3875745N
1967 Chevelle 3894939NF
68-69 Chevelle 3917124NF
1969 Chevelle 3959038NF
70-72 Chevelle 3969278NF

As always, there will most likely be some rumor of overlap in numbers but unless you have a build sheet/Protect-O-Plate and can verify the stamped codes as original, who knows? It should also be noted that the 1965 12-bolt is the only one with the diagonal bracing on the center section casting.

Note: Thanks to David Bates for the above information!

According to an old article, Inside '64 -- '72 A-Bodies, (Car Craft Magazine), 1967 was a transition year in that A-body cars might have a 1964-66 style rear end, a 1968-72 rear end (which is wider, and commonly available), or a "hybrid" rear end, which will have the 60.5-inch width, but with the early spring mounting pad and trailing arm brackets. Several late 1966 rear ends with casting number 3875745, one dated L 8 6 (December 8, 1966), have been found in early 1967 Chevelles and retain the retention plates to secure the rear springs.

https://www.chevellestuff.net/tech/rear_end_widths.htm

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post #19 of 42 (permalink) Old May 16th, 19, 12:48 PM
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Re: 12 bolt from hades

Quote:
Originally Posted by 2cool View Post
I was thinking the shock mounts were in he wrong place at least compared to my 69, look a the 67 above then look at Beth's pics.
The shock mount on beths is not in oem location somebody has moved them. Regardless of year they should look as on Gregs.
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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
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post #20 of 42 (permalink) Old May 16th, 19, 1:47 PM Thread Starter
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Re: 12 bolt from hades

Quote:
Originally Posted by Malibu ss 64 View Post
The shock mount on beths is not in oem location somebody has moved them. Regardless of year they should look as on Gregs.
I'm pretty sure the 66-67 shock mounts are only 1" away from the backing plate while 68-72 are about 3" away.

I think Saltherring is correct; the coil spring mounts are all that need to be fixed on the 69 rear end I have.

But I could be wrong LOL

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #21 of 42 (permalink) Old May 16th, 19, 1:49 PM Thread Starter
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Re: 12 bolt from hades

Quote:
Originally Posted by Kirk's67SS View Post
Beth if I lived closer you could have my old 67 12 Bolt

You installed a S60 , correct ? They are the ticket for drag racing for sure.
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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 #22 of 42 (permalink) Old May 16th, 19, 2:01 PM Thread Starter
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Re: 12 bolt from hades

Quote:
Originally Posted by Malibu ss 64 View Post
The 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.
The question I am struggling with is this : will using a later model rear end de-value the car ?
Is saving $300 now short-sighted ?

The car is going to be a driver for sure with a 489 and 6 speed T56. But everything to the eye will appear stock. That's why I'm not considering a Moser or S60 rear.

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #23 of 42 (permalink) Old May 16th, 19, 2:30 PM
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Re: 12 bolt from hades

Quote:
Originally Posted by nashville beth View Post
I'm pretty sure the 66-67 shock mounts are only 1" away from the backing plate while 68-72 are about 3" away.

I think Saltherring is correct; the coil spring mounts are all that need to be fixed on the 69 rear end I have.

But I could be wrong LOL
The only difference is that the axle tube is 0.5” longer on each side outside the brackets all brackets are located same but on later houses theres 0.5” extra clearance to the backning plate.

The shock mount on your 12 bolt is moved and not in oem location. Oem they are a reinforcement if the lca bracket, so it can be vise to put it back where it belongs.

Since its not a nr matching car I think the value wont be affected much if all with a later rear as long as you fix the spring mounts and have it rebuilt. If only a driver you can save money and reuse your current ends and go with c-clip axles.
If you want the narrow version othervise just use 68-72 axles and leave it. Theres info telling that 67 used narrow housings with flat 65-66 spring mount and 68-72 wider housings with 68-72 spring mounts+ a narrow hybrid version with 68-72 spring mounts. I cant verify if true or not?

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

Last edited by Malibu ss 64; May 16th, 19 at 2:55 PM.
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post #24 of 42 (permalink) Old May 16th, 19, 2:33 PM
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Re: 12 bolt from hades

Compare Gregs with this eBay listing of a68-72 12 bolt and you will see how they look unmolested.
https://www.ebay.com/itm/Original-19....c100930.m5375

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 #25 of 42 (permalink) Old May 16th, 19, 3:26 PM Thread Starter
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Re: 12 bolt from hades

Quote:
Originally Posted by Malibu ss 64 View Post
Compare Gregs with this eBay listing of a68-72 12 bolt and you will see how they look unmolested.
https://www.ebay.com/itm/Original-19....c100930.m5375
Yeah, I don't know where those brackets came from on my current 69-70 rearend.
Strange indeed.

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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post #26 of 42 (permalink) Old May 16th, 19, 3:35 PM
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Re: 12 bolt from hades

Quote:
Originally Posted by nashville beth View Post
The question I am struggling with is this : will using a later model rear end de-value the car ?
Is saving $300 now short-sighted ?

The car is going to be a driver for sure with a 489 and 6 speed T56. But everything to the eye will appear stock. That's why I'm not considering a Moser or S60 rear.
I wouldn't worry about devaluing the car if you are installing a T56. Having the wrong rear end in it isn't going to matter.


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post #27 of 42 (permalink) Old May 16th, 19, 6:03 PM
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Re: 12 bolt from hades

Quote:
Originally Posted by nashville beth View Post
I'm pretty sure the 66-67 shock mounts are only 1" away from the backing plate while 68-72 are about 3" away.

I think Saltherring is correct; the coil spring mounts are all that need to be fixed on the 69 rear end I have.

But I could be wrong LOL
I was not correct, Beth. I just did what I should have done before posting and that is go to the shop and measure the '69 rear that I have on the shelf. The inboard edge of the shock mount is approximately 1 3/4" from the inside surface of the axle flange. Sorry for the confusion.
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post #28 of 42 (permalink) Old May 16th, 19, 6:24 PM Thread Starter
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Re: 12 bolt from hades

Quote:
Originally Posted by Saltherring View Post
I was not correct, Beth. I just did what I should have done before posting and that is go to the shop and measure the '69 rear that I have on the shelf. The inboard edge of the shock mount is approximately 1 3/4" from the inside surface of the axle flange. Sorry for the confusion.
10-4 , no problem.

That S60 sure does look tempting - $2900 with the true trac center

https://www.strangeengineering.net/p...g-mounts.html/
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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 #29 of 42 (permalink) Old May 16th, 19, 6:48 PM
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Re: 12 bolt from hades

Quote:
Originally Posted by nashville beth View Post
10-4 , no problem.

That S60 sure does look tempting - $2900 with the true trac center

https://www.strangeengineering.net/p...g-mounts.html/
Yes, that does look nice. My '69 had a '67 rear in it when I bought it. The rear had a near new Eaton posi carrier with near new 3.73 gears, Strange Axles and C-clip eliminators. I sold it last fall for $2,000 minus brakes, as the buyer was going with discs on the rear of the '65 wagon he was installing it in.

Before removing/selling the '67 rear, I purchased a '69 3.55:1 rear that had been changed out to 4.88:1, by using a ring gear spacer. I replaced those gears with 3.73:1 and that is what I am presently running in the '69.

Given the cost for parts, (housing, gear set, carrier, pinion yoke, axles, small parts, etc.) professional set-up, axle tube straightening and what ever else you might need, it might be the right choice to buy the Strange set-up.
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post #30 of 42 (permalink) Old May 16th, 19, 8:15 PM Thread Starter
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Re: 12 bolt from hades

Quote:
Originally Posted by Saltherring View Post
Yes, that does look nice. My '69 had a '67 rear in it when I bought it. The rear had a near new Eaton posi carrier with near new 3.73 gears, Strange Axles and C-clip eliminators. I sold it last fall for $2,000 minus brakes, as the buyer was going with discs on the rear of the '65 wagon he was installing it in.

Before removing/selling the '67 rear, I purchased a '69 3.55:1 rear that had been changed out to 4.88:1, by using a ring gear spacer. I replaced those gears with 3.73:1 and that is what I am presently running in the '69.

Given the cost for parts, (housing, gear set, carrier, pinion yoke, axles, small parts, etc.) professional set-up, axle tube straightening and what ever else you might need, it might be the right choice to buy the Strange set-up.
Yes, it does seem no matter which direction we choose, the cost of a good setup is around $3000.

At least the Strange would be bulletproof. My T56 is going to be the weak link.

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, 12 bolt, Marina Blue with black interior
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