[PonchoV8]

I located a 12 bolt in a GP that may be original to the car.
(1) Will that year fit the GTO correctly?
(2) Also, is it a Pontiac specific number for that year?
(3) If so, what is that number so I can verify that it's a Poncho?
I have Chevy 12 bolts, but no Pontiac 12 bolt.
(3) Will 75-76 rears fit earlier GTO?

Thanks,

[Matt Meaney]

'70-'72 Gp is the same as GTO, with the same codes. '73 and later are different.

[1971WARBIRD]

okay you don't want a pontiac 12 bolt.the pontiac used bolt on axles and a weaker center section.there is also very little in parts for the pontiac/olds rear end.i have found both chevy and pontiac under GP's

the GTO's used chevy 12 bolts just like their Chevelle brothers.the pontiac one will bolt in but be weaker and have less parts to work with.

been there before.know a guy that got rid of one because he couldn't find parts to fix it.

[PonchoV8]

Ouch. I don't want that. But the restoration market value has to be something worth saving, no?

[1971WARBIRD]

check it close,it could be the better chevy.if it has c clip axles it's the good one.

you might be better to ask on the GP threads what it is worth.

[Matt Meaney]

the 455 Gp's used the c-clip 8.875" ring gear 12 bolt like the GTO and chevelle. i have a code XT rear out of a '71 455 Gp. it would be best to inspect the rear you're interested in to determine what it is exactly.
http://www.wallaceracing.com/cgi-bin/axle.cgi

while i've never seen it personally, i have heard of 400 cars getting 12 bolts also. maybe these are the smaller ones like the buick/olds units? the buick/olds 12 bolts use 8.5" ring gears and bolt in axles. from what i've read elsewhere on this forum, they are quite strong and have good parts availability.

[Matt Meaney]

the Gp rears where limited to 3.07 and 3.31 gears. i've seen open 3.07 geared rears advertised for $450. i got my 3.07 posi for $200 a few years back. fwiw.

[PonchoV8]

The engine was plucked long ago, so I don't know what it was orginally. Probably a 455 car since it's gone and there's a 12 in the back. The 'O' 12 bolts have a flat cover--at least the early ones did. This one has the Chevy 'eyebrow' cover, which is why I want it.
I would think the value would be higher in the GTO forum readers above the GP forum--since the GP is less desirable and someone might have the need in a GTO for a GT-37 455HO maybe? I've paid $200 for open 12s, but could've bought complete Monte Carlos with them AND disc brakes for $150 just a few yrs back. I just didn't have the will to pull the cars out of that yard and part them at the time. I've paid quite a bit less for them too, but maybe missing an axle or both.

[1971WARBIRD]

that sounds like the better 8.875(chevy)12 bolt.yes it would probably bring more here in the GTO threads.if it was the smaller it would be better off in the GP's more than likely.

haven't checked in a while.there used to be a small one in a 70 400 GP at a wrecking yard down the road.i liked the idea of the bolt on axles,but had trouble finding gears and posi units so gave up on it.was told the standard 10 bolt was just as strong.just what i was told.

[Steve Barcak]

"okay you don't want a pontiac 12 bolt.the pontiac used bolt on axles and a weaker center section.there is also very little in parts for the pontiac/olds rear end.i have found both chevy and pontiac under GP's....."


Not true. Not sure where you are getting your info from but, you are wrong. Perhaps you are reading something out of a book?
I know from experience that all the '70-'72 GP/GTO 455 12 bolts I have seen and owned over 30 years are identical to the 12 bolt chev except for the yoke which uses u bolts where the chev uses straps and bolts.

I've looked at dozens of these cars since the mid 70s and have owned and or currently own about a dozen myself. All of them use c clips. Only the olds has the round cover and does not use c clips.
A Pontiac 12 bolt is a very desirable rear to have and all the chev parts fit in it. I have put 12 bolt chev posi units in a few Pontiac 12 bolt rears. There are the same.

Steve

Hosting 11th annual Pontiac Heaven, show, swap, drags, party and all around good time. Saturday April 4, 2009 at Speedworld near Phoenix, Az
more info- www.pontiacheaven.org
Also hosting- 7th annual Nostalgic Show and Go! and swap. Drags, cool car show, parade, special exhibitions, gassers, rails, stockers, customs and much more. coming Sunday April 5, 2009 to Speedworld. Phoenix, Az -This is Arizonas longest continuest running nostalgic event, our 7th year! www.nostalgicshowandgo.org

[PonchoV8]

The max that I should expect it priced at--this 71-72 ish GP 12 bolt rear?

I also know of a 75-76 455 GP. Were they 12 bolts? I know someone said they're different, but it might be worth grabbing if it's worthy to someone with one.

[Steve Barcak]

The 12 bolt chev/pont that we are discussing was last used in 1972 and started in 1965.

Steve

Hosting 11th annual Pontiac Heaven, show, swap, drags, party and all around good time. Saturday April 4, 2009 at Speedworld near Phoenix, Az
more info- www.pontiacheaven.org
Also hosting- 7th annual Nostalgic Show and Go! and swap. Drags, cool car show, parade, special exhibitions, gassers, rails, stockers, customs and much more. coming Sunday April 5, 2009 to Speedworld. Phoenix, Az -This is Arizonas longest continuest running nostalgic event, our 7th year! www.nostalgicshowandgo.org

[PonchoV8]

Yeah, me too. How much should I expect one to priced at? Similar to the Chevy?

So later rears weren't the 12 bolt design even when using the 455 in the GP I assume?

EDIT: According to Ron's Pontiac Site the GP had three available ratios in 12 bolt. 3.07, 3.31 and 3.55. No 12 bolts later are listed.
http://ronspontiacpage.com/reference...arendcodes.htm

[1971WARBIRD]

Originally Posted by Steve Barcak

"okay you don't want a pontiac 12 bolt.the pontiac used bolt on axles and a weaker center section.there is also very little in parts for the pontiac/olds rear end.i have found both chevy and pontiac under GP's....."


Not true. Not sure where you are getting your info from but, you are wrong. Perhaps you are reading something out of a book?
I know from experience that all the '70-'72 GP/GTO 455 12 bolts I have seen and owned over 30 years are identical to the 12 bolt chev except for the yoke which uses u bolts where the chev uses straps and bolts.

I've looked at dozens of these cars since the mid 70s and have owned and or currently own about a dozen myself. All of them use c clips. Only the olds has the round cover and does not use c clips.
A Pontiac 12 bolt is a very desirable rear to have and all the chev parts fit in it. I have put 12 bolt chev posi units in a few Pontiac 12 bolt rears. There are the same.

Steve
www.nostalgicshowandgo.org

this could all be a name thing.i have always been told the 8.875 ring gear 12 bolt was a chevy rearend and the smaller one was the olds/pontiac.we never called the 8.875 12 bolt in a GTO a pontiac rearend.

there were at least 2 in GP's at a yard just down the road that i go to all the time.they were both the smaller bolt in axle style.i sold one to a guy doing a lemans hot street car,but he got rid of it after not being able to get the parts he wanted,and Mike changed his after not being able to get new spider gears after breaking his.

the 455 thing makes sense as all GTO's with 455's used the chevy 12.not sure what motor those 2 GP's had or what the one i got mine came from.Mikes was from a Ralley 350 if i remember right.

i think you would agree that the 8.875 is alot better rearend than the olds,thats mostly what i was getting at.