12 bolt rear end

[Brinson Pachar]

I currently have a 10 bolt rear under my 70 GTO. I have found a 12 bolt posi from either an early chevelle I believe. It measures 1" shorter between the backing plates than the 10 bolt does. I believe the tires will clear the inner fenders. Is there any thing else to
consider? All the spring perches and control arm mounts seem to be in the right places.
Any help would be appreciated.

[Brinson Pachar]

I currently have a 10 bolt rear under my 70 GTO. I have found a 12 bolt posi from either an early chevelle I believe. It measures 1" shorter between the backing plates than the 10 bolt does. I believe the tires will clear the inner fenders. Is there any thing else to
consider? All the spring perches and control arm mounts seem to be in the right places.
Any help would be appreciated.

[Big Injun]

You have located an early Chevelle (64-66) 12-bolt. Yes it is 1" narrower. You did not state what wheel you are running on your car. The Rally II's will have no problem. If you are going to an aftermarket wheel, you'll need to measure for the correct back spacing. I believe you will not want more than 4.5"

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www.PontiacDragDays.com (http://www.PontiacDragDays.com)
Dave "Big Injun" Anderson

[roger van doren]

I have a 12 bolt that needs a gear upgrade,so I need a series 3 carier and some 373 gears,
I need the carier more than the gears.
thanks roger

[Jack Ferris]

Years ago i tried to swap a 12 bolt from a 66
chevelle into my 69 GTO and the spring perches were off a bit. You may want to look into it.

[JC455]

You might want to contact Hotchkiss Performance (www.hotchkiss.net (http://www.hotchkiss.net)) on this subject. I may be wrong, but I believe you're going to need adjustable upper control arms to compensate for the pinion angle (I think the upper arms are shorter on the 64-66 cars)

My two cents


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John

[Paul Spotts]

Big Injun is correct on rear. The rear's are all the same bracket wise.(64-72 A-body wise)The upper control arms are different because of the frame changes - in other words you use the upper arms for your year vehicle - not the rear. The lower arms are all the same (length wise)Control arm bushing condition is important. The u-joint is different - but a conversion u-joint is available. Also beware of the Oldsmobile 12 bolt - It is not the same as the Chevy 12 bolt - The Olds has a round rear end cover - with no protrusion like the Chevy. Olds 12 bolts use 10 bolts on ring gears - not as strong.

[Scott Misus]

Jerry:

One item that Paul didn't include was the fact that a rear yoke from a '69-70 big car can be used on the 12-boat. This will eliminate the need for a conversion U-joint.

[This message has been edited by Scott Misus (edited 01-02-2000).]

[Brinson Pachar]

Thanks, guys you've been a big help. I really
like the new forum!!!

Brinson