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Old 05-24-2011, 08:22 AM   #1
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What 12 bolt rear ends will fit my 3rd gen?

I am looking into swapping out my 10 bolt for a 12 bolt. Are there any direct swap 12 bolt rearends? What type of car are they found in?
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Old 05-24-2011, 08:33 AM   #2
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Re: What 12 bolt rear ends will fit my 3rd gen?

None will fit a 3rdgen car. If they did, everyone on this site would be braging about their 12-bolts. Do you see any Posts about them. That is your answer.
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Old 05-24-2011, 08:50 AM   #3
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Re: What 12 bolt rear ends will fit my 3rd gen?

What makes them not fit? Length of rearend? Size of carrier housing?
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Old 05-24-2011, 09:36 AM   #4
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Re: What 12 bolt rear ends will fit my 3rd gen?

Biggest problem I think is the lack of a torque arm mount.
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Old 05-24-2011, 12:03 PM   #5
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Re: What 12 bolt rear ends will fit my 3rd gen?

Moser or Strange. Either way, around $2000.
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Old 05-24-2011, 12:36 PM   #6
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Re: What 12 bolt rear ends will fit my 3rd gen?

Quote:
Originally Posted by chevysquid View Post
Biggest problem I think is the lack of a torque arm mount.
I agree. If you wanted to convert one it would be easy enough to weld your springs, lcas, and etc on, but you'd have to make your own tq arm mount or your own torque arm to mount off your mounting tabs. The 10 bolt and 9 bolts are cast into the housing itself.

$2000+ without most options for aftermarket ones. Aftermarket ones normally provide you the new bracket (at least on the 9"s) to accept the torque arm or provide mounting ears on the housings and a different tq arm. You still have to make sure the bracket or bolt attachments are correct and sturdy. I've read about companies using shorter bolts and they eventually came loose got slop in the bracket on the tq arm and broke it. The tq arm provides the correct pinion angle without it the rear will pivot and tear up stuff (driveshafts, floor pans, etc).

Last edited by fireturd350; 05-24-2011 at 12:41 PM.
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Old 05-24-2011, 05:26 PM   #7
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Re: What 12 bolt rear ends will fit my 3rd gen?

The lack of a torque arm mount is the biggest issue but if can overcome that by fabricating something to work or change the rear suspension to something like ladder bars, your next issue will be width. The car 12 bolts are different than the truck 12 bolts. The car 12 bolt is actually stronger. Most 12 bolts you'll find in the junkyard are from trucks and will be too wide. The closest 12 bolt that will be the proper width would be from a first gen f-body or Nova etc. Chances are if you could find one, you could sell it for enough to buy an aftermarket bolt in diff. I'm not sure if any of the second gens had a 12 bolt option but they would be just as valuable.
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Old 05-26-2011, 04:45 PM   #8
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Re: What 12 bolt rear ends will fit my 3rd gen?

Now to long ago my '86 got a 12 bolt fabbed in. here are the pics
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Old 05-26-2011, 07:56 PM   #9
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Re: What 12 bolt rear ends will fit my 3rd gen?

Installing the spring, shock, LCA mounts etc is the easy part. Do lots of measurements then cut them off a donor 10 bolt and weld them onto the replacement diff. Any picks of what you did about the torque arm? Looks like a G-body diff with the factory triangulated 4-link mounts on top.
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Old 07-07-2011, 09:49 AM   #10
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Re: What 12 bolt rear ends will fit my 3rd gen?

This is a nice set up you fabbed, any other pics? I was going to do this in my 85 years ago which I have since sold, an early Impala is the correct width more or less backing plate to backing plate so that is a good candidate

What rear did you use?

We will soon do a swap like this into my friends blown 383 6 speed TA that we are about to put together..

Regards, Tim
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Old 07-07-2011, 12:56 PM   #11
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Re: What 12 bolt rear ends will fit my 3rd gen?

Quote:
Originally Posted by Big454blockchevy View Post
Now to long ago my '86 got a 12 bolt fabbed in. here are the pics
this is all worthless without pics/info of what you did to install the torque arm....
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Old 07-07-2011, 03:44 PM   #12
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Re: What 12 bolt rear ends will fit my 3rd gen?

Quote:
Originally Posted by AlkyIROC View Post
I'm not sure if any of the second gens had a 12 bolt option but they would be just as valuable.
The second gen 8.5" 10 bolt is still a good strength upgrade, and is something like .5" off of exact width. Problem of torque arm still exists, but at least this rear is close. Bolt pattern for wheels is the same too.
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Old 07-07-2011, 03:58 PM   #13
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Re: What 12 bolt rear ends will fit my 3rd gen?

Quote:
Originally Posted by AlkyIROC View Post
The car 12 bolts are different than the truck 12 bolts. The car 12 bolt is actually stronger. Most 12 bolts you'll find in the junkyard are from trucks and will be too wide. The closest 12 bolt that will be the proper width would be from a first gen f-body or Nova etc. Chances are if you could find one, you could sell it for enough to buy an aftermarket bolt in diff. I'm not sure if any of the second gens had a 12 bolt option but they would be just as valuable.
I'm not sure if it was '70 only, but an early 2nd gen 12-bolt did exist and is the same width as a 68-72 A-body (which are semi-easy to swap into a leaf 2nd gen.)

The narrower 1st gen rears are the same width as the 64-67 A-body.
Quote:
Originally Posted by AlkyIROC View Post
Installing the spring, shock, LCA mounts etc is the easy part. Do lots of measurements then cut them off a donor 10 bolt and weld them onto the replacement diff. Any picks of what you did about the torque arm? Looks like a G-body diff with the factory triangulated 4-link mounts on top.
Not with those big axle tubes and wide-spread UCA bushing mounts it doesn't.
Quote:
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this is all worthless without pics/info of what you did to install the torque arm....
The '87 Buick GNX (not the Grand National) had two attachment points on it's cast rear cover for the torque arm. It would be straightforward to duplicate that for the 82-02 F chassis. Fun thread re: this topic matter here: http://www.thirdgen.org/techboard/tr...5-swap-go.html
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Old 03-06-2012, 01:23 PM   #14
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Re: What 12 bolt rear ends will fit my 3rd gen?

What 12 bolt did you use? I am guessing a 68 - 72 Chevelle? which is the same width as a mid 70s Camaro 8.5 corporate 10 bolt...I am thinking this may be the way to go, what is the overall width when measured inside the backing plate to the other backing plate?

thanks, Tim
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Old 03-06-2012, 01:27 PM   #15
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Re: What 12 bolt rear ends will fit my 3rd gen?

I just sent this pic to my friend, so that he can measure up the rear axle tonight...would be great to know what your 12 bolt meaures, this is what I meant about the inside width - any help would be greatly appreciated. i am not worried about fabbing the torque arm mount etc, as I do a lot of welding and fabrication, lucky to have a mig, tig, arc welder, chop saw, plasma cutter etc

Click the image to open in full size.

Last edited by BOSTONCAMARO; 03-06-2012 at 01:30 PM.
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Old 03-07-2012, 12:19 PM   #16
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Re: What 12 bolt rear ends will fit my 3rd gen?

The 1970 Trans am came with a 12 bolt and 70-72 camaros had a 12 bolt in the Z28 and big block cars if memory serves. The second gen 10 bolt is a great rear and the 79-81 trans ams came with posi rear disc. All 80-81 turbo trans ams came with posi rear disc brake rears. I think it was code J65 and the WS6 cars came with posi disc brakes. In 79 they were ordering so many they almost ran out and so they made a WS7 code which meant everything a WS6 had except rear disc. I have two 81 Z28s with posi rear disc brake rears out of trans ams and I have never had a problem out of them. I have blown up more turbo 350 transmissions than anyone alive but never lost a rear. I think the ford 9 is probably the best since you can change center sections so easy and I have one in my 89 iroc with a locker and it is great.
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Old 03-07-2012, 09:46 PM   #17
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Re: What 12 bolt rear ends will fit my 3rd gen?

My dad saw a 12 bolt for a 68-72 Chevelle online tonight, we went to look at it.....as my dad and I wheel and deal with some parts etc....could believe my eyes....it was all set up for a 3rd generation Camaro/Firebird. Only thing that was not fabbed yet was the torque, so we will do that, then will go in my friends car.
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Old 10-24-2013, 06:13 AM   #18
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Re: What 12 bolt rear ends will fit my 3rd gen?

Quote:
Originally Posted by abray1 View Post
The 1970 Trans am came with a 12 bolt and 70-72 camaros had a 12 bolt in the Z28 and big block cars if memory serves. The second gen 10 bolt is a great rear and the 79-81 trans ams came with posi rear disc. All 80-81 turbo trans ams came with posi rear disc brake rears. I think it was code J65 and the WS6 cars came with posi disc brakes. In 79 they were ordering so many they almost ran out and so they made a WS7 code which meant everything a WS6 had except rear disc. I have two 81 Z28s with posi rear disc brake rears out of trans ams and I have never had a problem out of them. I have blown up more turbo 350 transmissions than anyone alive but never lost a rear. I think the ford 9 is probably the best since you can change center sections so easy and I have one in my 89 iroc with a locker and it is great.
so you're saying i can use a ford 9 for a strong change to the stock 89 rs rear? I need help finding out what i can do.
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Old 10-24-2013, 06:13 AM
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