#21  
Old 09-22-2021, 07:07 PM
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Not sure about those 8.2s and high HP motors. In my class in the old NMCA was John McWhirter(an original Comp Cams owner) and his 66 or 67 tripower 442 stick car. It had been a race car since new. He ran high 11s with it, most of us in the class low 12s. BUT there was a 25% chance he would break the rear, and you would win usually gears until he started having them re heat treated.

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1964 Impala SS 409/470ci 600 HP stroker project
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  #22  
Old 09-22-2021, 09:51 PM
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My high torque totally STOCK 389 1966 GTO stock tires 4speed broke the spider gears one time when I hit second gear, So there's that

Yeah I drove it hard but but again it was totally stock on street tires never could afford slicks barely afforded gasoline 1976

I drove it like a pissed off teenager Ha I was.


Last edited by Formulas; 09-22-2021 at 10:08 PM.
  #23  
Old 09-23-2021, 05:26 AM
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Quote:
Originally Posted by Scarebird View Post
Another option OPH may explain better than me is a 1971-72 Olds or Buick A 8.5"; superior to a 8.2 but cheaper than a 12 bolt and you get bolt in axles.

I have one in my 71 with a Detroit TruTrac.

IIRC you may need to mod the prop shaft.
I have a 12/10 bolt 8.5" Olds rear in my car. Has taken a tremendous beating. Countless 4-speed miles. Over 400 passes on slicks, etc. Still going! I did put fresh clutch plates and heavier springs in it years ago.

  #24  
Old 09-23-2021, 10:27 AM
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Quote:
Originally Posted by Kenth View Post
1966-72 Pontiac A-body uses the same rearend width.
1964-65 was 1" narrower overall width.
^^This.
Many think that all the 64-67 rears were narrower than the 68-72, (BOP 8.2), but this is not the case. Only the 64-65.
Also, it has been said many times that there is an early 66 rear that is narrower than the late 66. All the 66 rears that I've seen from Pontiac A-bodies were same width as 67-72. Seems like Pontiac would have documented any part number changes during the 66 model year if that were the case.

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  #25  
Old 09-23-2021, 07:31 PM
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So if only 64-65 were shorter was the a "short" 12 bolt? I would thin GM/Chevy would not put a 12 bolt in since unless you got a rare 65 396 Chevelle would have just been a 283 or 327 in it.

What is the flange to flange length of short and "regular" length A body rears? I thought the "regulars" were the same width as second gen as the axles length is the same.

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1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #26  
Old 09-23-2021, 08:33 PM
'ol Pinion head 'ol Pinion head is offline
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Quote:
Originally Posted by Skip Fix View Post
So if only 64-65 were shorter was the a "short" 12 bolt? I would thin GM/Chevy would not put a 12 bolt in since unless you got a rare 65 396 Chevelle would have just been a 283 or 327 in it.

What is the flange to flange length of short and "regular" length A body rears? I thought the "regulars" were the same width as second gen as the axles length is the same.
The early Malibu/Elco/Chevelle 12 bolts were first installed in '65 Chevy A-bodies behind Chevys 4bbl small block engines. 6 cyl & 2 bbl V8 cars received an 8.2 Chevy rearends ...different than early BUICK 8.2's & early Pontiac 8.2's. This width of 12 bolt & 8.2 Chevy 10 bolt A-body rearend continued through '67 production. One of the rarest, & most expensive factory 12 bolt rears ever built was used in the 201 '65 Z16 Chevelles. Main difference, c-clip axle housing ends took a bigger diam axle.

The '64 & '65 & very early 1966 PONTIAC 8.2 10 bolt rears & the '64 & '65 BUICK 8.2 are also of the narrow variety. Have pulled numerous "short" Pontiac 8.2 10 bolt axles out of original housings installed in early '66 model Pontiac Tempest & LeMans. In the late 80's through the 90's in the country yrds, crusher yards, & early Pick-N-Pulls, I routinely pulled used sealed bearing axles out of '64-69 GM A-body rears. Sealed axle bearing axles have an eventuality where the bering seizes & chew up the axle mating surface, I've literally cut the bearing collars off a TON of original sealed axle bearing axles.

'68-72 Chevy 12 bolt A-body rears share the same width axles as the '70 F-body 12 bolt axle. McKinnon plant 12 bolt A-body rears were assembled with their own specific c-clip axle, different style backing plates for non Chevy applications, as well as 3R pinion flange.

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Last edited by 'ol Pinion head; 09-23-2021 at 08:39 PM.
  #27  
Old 09-23-2021, 08:50 PM
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Originally Posted by 'ol Pinion head View Post
The '64 & '65 & very early 1966 PONTIAC 8.2 10 bolt rears & the '64 & '65 BUICK 8.2 are also of the narrow variety. Have pulled numerous "short" Pontiac 8.2 10 bolt axles out of original housings installed in early '66 model Pontiac Tempest & LeMans.
On the early 66’s with the narrow housing, what would you say the months of production were before they installed the wider rear? Sept thru oct? Nov? Were they from a certain assembly plant?

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  #28  
Old 09-23-2021, 08:58 PM
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Originally Posted by Singleton View Post
^^This.
Many think that all the 64-67 rears were narrower than the 68-72, (BOP 8.2), but this is not the case. Only the 64-65. Also, it has been said many times that there is an early 66 rear that is narrower than the late 66. All the 66 rears that I've seen from Pontiac A-bodies were same width as 67-72. Seems like Pontiac would have documented any part number changes during the 66 model year if that were the case.
All I can relate Singleton is if you pulled enough original '66 Pontiac 8.2 axles, you would have run across a few factory installed early '66 rears of the shorter variety. After jacking up the frame of A-body yard cars, I've always shined a flashlight at the center housing as well as up between the brake backing plate & the lower control arm perch. Only one finger would fit, bingo, early style A-body rear. Two fingers fit, a wider style. Years ago, I actually pulled several '66 3.55 coded STT rears out of two country yards, all were bought cheap as the axles were missing. Yard owner or worker had prev pulled & sold the axles out of them. No problem as in stock I had a fair supply of nice original axles, cked #1 condition, with new studs w RW507C's installed.

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Last edited by 'ol Pinion head; 09-23-2021 at 09:25 PM.
  #29  
Old 09-23-2021, 09:24 PM
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Quote:
Originally Posted by Singleton View Post
On the early 66’s with the narrow housing, what would you say the months of production were before they installed the wider rear? Sept thru oct? Nov? Were they from a certain assembly plant?
Singleton, most of the '66 & 67 Pontiac A-body's in my region that didnt wonder far were built out of Kansas City plant. Occasionally I would run across the errant Fremont builds & every once & a while a '66 or 67 driven down from up North (mainly Baltimore builds). The prev Northern drivers usually came during the first "Oil Boom" (mid 70's-82). By the early '90's I was heavily chasing parts & "cleaning" yards of many specialty core items. Unless I had serious interest from a restoration point, I did not make note of core parts like loose axles.

From a research pt of view, in the mid 80's a good friend & I began noting the VIN's, cowl tag numbers & accessory codes & presence of factory options on every '66 & 67 GTO & '67 Firebird we ran across in boneyards, private stashes, & elsewhere. Part of the impetus was from an article in an '86 Super Chevy magazine, where many of the accessory codes for early ChevyII's were decoded. This peaked our interest, as we recognized that many of these Fisher Body accessory codes were shared with other bodystyles. I believe this article also gave Pete McCarthy the impetus to study & publish a comprehensive list of accessory codes by '89 or '90.

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  #30  
Old 09-23-2021, 09:32 PM
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drewm check your PMs

  #31  
Old 09-23-2021, 09:37 PM
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Quote:
Originally Posted by Skip Fix View Post
So if only 64-65 were shorter was the a "short" 12 bolt? I would thin GM/Chevy would not put a 12 bolt in since unless you got a rare 65 396 Chevelle would have just been a 283 or 327 in it.

What is the flange to flange length of short and "regular" length A body rears? I thought the "regulars" were the same width as second gen as the axles length is the same.
Yes there was a shorter 12 bolt that GM used up through 1967 A bodies. 68 they got wider to accommodate the new larger A-body.
Width was the same on the 12 bolts from 64-67 and they were installed in Abodies with the 327/300hp if optioned with 4 speed and the 327/350 hp Chevelles (all were 4 speeds) as well as all the 396 cars.

I have both versions here but I'd have to do some digging to get any measurements, they are stacked on top of each other like cord wood. I can tell you the width of the 68/72 A-body 12 bolts are exactly the same as 2nd gen 70-71 F-body 12 bolts, or 2nd gen 10 bolts for that matter. I have those versions here as well. I had to rob an axle from one of the 2nd gen F-body 12 bolts for my Chevelle 12 bolt one time when it had a bearing go south. Direct replacement.

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  #32  
Old 09-23-2021, 09:49 PM
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Quote:
Originally Posted by 'ol Pinion head View Post
I've always shined a flashlight at the center housing as well as up between the brake backing plate & the lower control arm perch. Only one finger would fit, bingo, early style A-body rear. Two fingers fit, a wider style.
I’ve always heard about the 1 finger, 2 finger way of measuring, but I feel like it’s not always accurate. Depending on the style of backing plate, it could easily fool someone as the pics below illustrate.
The black painted rear is a 64, the rusty one is a 66. Because the 66 has an extra flange on the inside of the backing plate, it has a 1” space between the lower control arm perch and the backing plate, same as the 64 with a smooth backing plate. Someone could assume that, if looking up from the ground, that both rears were the same width, (narrow). But the 66 rear is actually 1” wider. In the other pic both backing plates are aligned together on one side and there is 1” difference in width on the other.
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  #33  
Old 09-23-2021, 09:56 PM
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Quote:
Originally Posted by Skip Fix View Post
Not sure about those 8.2s and high HP motors. In my class in the old NMCA was John McWhirter(an original Comp Cams owner) and his 66 or 67 tripower 442 stick car. It had been a race car since new. He ran high 11s with it, most of us in the class low 12s. BUT there was a 25% chance he would break the rear, and you would win usually gears until he started having them re heat treated.
I always cringed watching this 66 W30 run with that 8.2 out back.

https://youtu.be/vPFTFsL1uzk

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  #34  
Old 09-24-2021, 03:52 AM
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In my MPC Revised 5-1-67 bying a rear axle shaft for 1966-67 T/6-T/8 youŽd get a #9784847 shaft.
1964-65 T/6-T/8 uses #9776793 axle shafts.
Only one housing assembly available 1966 spare part-#9784925.

No notes whatsoever on an "early" 1966 shaft or housing assembly.

Finding a "short" 8,2" on a 1966 A-body may be due to owner was a racer and wanted wider rear tires inside fenders and replaced the wider original rear end?
Who knows what happened 50+ years ago, probably more than we will ever know.
OPH, do you have casting numbers on the "early shorter" 1966 rear end?

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  #35  
Old 09-24-2021, 09:52 AM
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I've got an early A body 12 bolt bolt on springs I am pretty sure is shorter than my second gen F body 10 bolt. I'll measure it this weekend and check the 1 finger rule!

I think 30-1/8" axles are what is used in second gen and 68+ A bodies.

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1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #36  
Old 09-24-2021, 01:18 PM
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Quote:
Originally Posted by Skip Fix View Post
I've got an early A body 12 bolt bolt on springs I am pretty sure is shorter than my second gen F body 10 bolt.
Yes it should be shorter if it's pre 68. Only the 68-72 A-body 12 bolt will be the same width as your 2nd gen F-body 10 bolt.

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  #37  
Old 09-24-2021, 01:58 PM
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Originally Posted by Formulajones View Post
I always cringed watching this 66 W30 run with that 8.2 out back.

https://youtu.be/vPFTFsL1uzk
JAY-Zuss!! First run I saw 2-3" of air under that left front tire! IMPRESSIVE!!!

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  #38  
Old 09-24-2021, 03:15 PM
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Originally Posted by geeteeohguy View Post
JAY-Zuss!! First run I saw 2-3" of air under that left front tire! IMPRESSIVE!!!
Yeah, that poor rearend, lol. That M20 with 4.33's out back help get it moving. If I remember right he was running a set of M&H DOT stickies on it which were legal for the stock class at that time.

Sac is 50 feet above sea level too so you typically run pretty good there if the air is ok. I raced there years ago, really liked that track. I don't think it's around anymore.

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Last edited by Formulajones; 09-24-2021 at 03:24 PM.
  #39  
Old 09-26-2021, 03:52 AM
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Contact Monzaz. I had him rebuild a 2.56 posi rear and a 3.23 posi 8.2 rear. Factory cone style. Both were completely trashed. Both laid down nearly identical twin stripes on the pavement after he redid them.

  #40  
Old 09-26-2021, 08:22 PM
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So my second gen 10 bolt is 56" at housing flanges, second gen 9" replacement housing(for the future) 56".
Early bolt on spring 12 bolt 54 1/2" and "one finger.
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1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
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