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64 gto with original engine and m-20 and cant figure out if rearend is original. Manifest says its 1-2-K in boxes 69-70-71. Rearend has 9788647 stamped on lower right corner of pumpkin webbing and GFD stamped on lower left corner of pumpkin. I do know its a 8.5 10 bolt from pictures on other sites. Cannot find any other numbers except a G and upsidedown 2 on drivers side axel tube. Tags and stickers and colors are long gone. The whole rearend is red primer in good condition but trailing arms etc are typical midwest rust. Any help? Thanks!
 

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'64 Pontiac A-bodys had the small upper control arm mount and the Pontiac 8.2 10 bolt gray iron cast center hsg should have casting #9773369. This particular housing is easily spotted by the casting number and the small cast mounts for upper control arm bushings. Buick also cast a small upper control arm mount '64 8.2 rear, but the early Buick 8.2 has it's own style casting and own casting number.

The next chronological Pontiac 8.2 10 bolt was cast 9773722, then there was the 9779822. All 3 of these Pontiac gray iron casting numbers one can find on the early (narrow) style Pontiac 8.2 10 bolts.

The 9788647 center hsg Pontiac 8.2 rear you have is a nodular iron housing Pontiac 8.2 10 bolt out of a '67 Pontiac A body. Most likely from a GTO, and factory assembled with 3.55 gearing and the 4 pinion Safe-t-track carrier. Much stronger rear than the original gray iron 8.2 10 bolt, but 1" wider, has the larger upper control arm bushings, and should have the fluted locator style coil spring mounts, not the '64-66 style that use the clamp on style coil spring attachment.

No 8.5 A body rears till '71 model, and even then not factory installed in Pontiacs. As a long time GM differential builder, and having helped popularlize the performance 8.5 A body build, have built many 8.5 A body rears for '64-66 A bodys. Have also had several customers that were into disquising these later HD 10 bolts to look just like earlier Pontiac 8.2 10 bolts.
 

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Wow thats more info than i imagined i would get and very fast too! Just got the gto last week and just joined the forum this morn. Thanks so much!!
 

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Sold that gto as it was way too much work and money for me. Now i have a totally restored tripower 4 speed numbers matching but the rearend doesnt fall into your description of original for a 64. Casting number 9783393 with L166 right above it and WF on passenger rear axle tube facing it from behind. Pic attached. Supposed to be original 3.55 safttrac. What do i really have?
 

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Sorry to jump in on your thread but since you have OPH talking about 64 rear ends I thought I'd ask if he knows what I have under my 64. The casting number on mine is 9777142.

Thanks!
Rick
 

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While we're on the subject, My rear casting # is 9792977. The Date code looks like B028? The B could be an 8? Not sure.. What do you think? This is also in a 64 Lemans BTW.
 
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