1968 GTO rear end question - Pontiac GTO Forum
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post #1 of 29 (permalink) Old 03-11-2013, 08:36 PM Thread Starter
 
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1968 GTO rear end question

Hey guys, I know this subject matter, rear ends, has probably been beat to death. But as we all know, 12 bolt rear ends are getting pricey out there. Anyways, I have a chance to get a 12-bolt rear end housing (without differential, gears and brakes) for a decent price.

My question is there is a difference in Pontiac rear ends versus other GM A-Bodies? I thought I heard that Pontiac, Olds, and Buick have a different rear end than Chevrolet, is that correct?

The "numbers are 40992 cant read very good 255 has R2 had 2.56 gears has C10 measures Flange to flange 55 3/8 long..All mounts look same as 70 Chevelle,, has Carrier Main Caps and bolts.I think these came in 68,69 Skylark,olds 442,Cutlass". Sorry, I am quoting seller here.

Is this a rear end just for Olds and/or Buick or can it be used on a Pontiac?
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post #2 of 29 (permalink) Old 03-11-2013, 10:14 PM
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You don't want the Olds 12 bolt. It still has 10 bolts on the ring gear and the "12 bolt" is in reference to the cover only.

Pontiac "10 Bolt" is superior in strength to it anyway. 12 bolt Chevy style is the strongest GM rear for these cars and many aftermarket companies offer the Ford 9" which is nice because it is strong, offers mucho gear ratio choices, brake options and superior axle bearings (no c-clips).

For ultimate strength consider the Dana 60 and now I hear Strange Engineering is offering a BIG 10" rear axle that will bolt in GM a body's.

It all depends on your goals and budget but I would say if you are starting from scratch check out Currie, Strange and others for a 9" Ford rear.
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post #3 of 29 (permalink) Old 03-11-2013, 10:25 PM
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With what the man said. The terms 10-bolt and 12-bolt refer to the number of bolts holding the ring gear onto the carrier, NOT the number of bolts on the cover. There are some type-O axles out there that have 12 cover bolts, but inside they're really just a weaker version of the 10-bolt.

This is what the "Type-O" ("pretend" 12 bolt cover looks like)


And here's what a 'real' 12 bolt cover looks like


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post #4 of 29 (permalink) Old 03-11-2013, 10:52 PM Thread Starter
 
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Thank you, thank you gentlemen. This information is exactly what I need to hear. I am going to pass on the Olds rear end. Instead, I am going to use that money to buy a factory endura bumper thatis straight and already prepped to be installed and painted (yes, I realize even with a factory endura bumper, that there will require sanding and fitting to make it fight right).
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post #5 of 29 (permalink) Old 03-11-2013, 11:27 PM
 
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Re: 1968 GTO rear end question

Remember, depending on what you have planned for your engine there's nothing wrong with a good old Pontiac 10 bolt with an Eaton or Auburn posi unit. Mine is running great so far
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post #6 of 29 (permalink) Old 03-12-2013, 08:08 AM
 
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Pontiac did use the Chevy 12 bolt rear ends in the 1970 455 GTO's and Grand Prix. I have one under my '68.
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post #7 of 29 (permalink) Old 03-12-2013, 08:39 AM
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Indeed. Unless you're making more than 500 lb. ft. of torque, and/or plan to make a habit out of dumping the clutch in a manual trans car, the factory 10-bolt in good condition ought to last for a good long while.'

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post #8 of 29 (permalink) Old 03-12-2013, 10:41 AM Thread Starter
 
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No, I am not planning on anything more than 450 HP and I am not a racer, but am more of a boulevard cruiser.

How do I know whether I have a Pontiac 10 bolt or just a GM 10-bolt (I know my current rear end is not original to car)? What are the differences between GM, Chevrolet, Buick/Olds and Pontiac rear ends (either 10 bolt or 12 bolt)?

If I get a Chevelle rearend (there is a 12 bolt from a 1969 Chevelle that is for sale locally), and want to or need to change differential, gears or axels, do I need to get Chevy parts or will Pontiac internals work on a Chevy/GM rear end?
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post #9 of 29 (permalink) Old 03-12-2013, 05:30 PM
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As far as I know, with the exception of the aforementioned "Type-O" axle, all the 10 bolts in GM cars from that era were pretty much the same. Hopefully someone who knows more than me will chime in here.

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post #10 of 29 (permalink) Old 03-12-2013, 07:03 PM
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Quote:
Originally Posted by mrvandermey View Post
No, I am not planning on anything more than 450 HP and I am not a racer, but am more of a boulevard cruiser.

How do I know whether I have a Pontiac 10 bolt or just a GM 10-bolt (I know my current rear end is not original to car)? What are the differences between GM, Chevrolet, Buick/Olds and Pontiac rear ends (either 10 bolt or 12 bolt)?

If I get a Chevelle rearend (there is a 12 bolt from a 1969 Chevelle that is for sale locally), and want to or need to change differential, gears or axels, do I need to get Chevy parts or will Pontiac internals work on a Chevy/GM rear end?
No parts will interchange between the Olds, Pontiac and/or Chevy rears. I have a 12 bolt in my car and put about $1500 into it to make it "right" including Strange Street C-clip eliminators and hardened axles; two must haves in my book because the 12 bolt uses the axle as the inner race for the bearing.
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