Forged vs. Cast Axle Identification (BOP 8.2)

93Octane
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Forged vs. Cast Axle Identification (BOP 8.2)

Postby 93Octane » Sun Oct 14, 2018 7:42 am

I have a Pontiac BOP 8.2, 67 model year (Dec 66) Safe-T-Track 3:23 rear (cone posi worn out) in my 71 GTO. It has the 3-hole flange axles in it which I understand are forged vs. the 1-hole versions which are cast. I recently put new Timken sealed bearings on them after one of the bearings grenaded. I also have a Pontiac BOP 8.2, 72 model year (Sep 71) Open Diff 3:23 rear I purchased a while ago that I planned to rebuild with a new cone posi unit for street use/street tires only and put into the car as a replacement as I believe the 70 up axle roller bearing design handles loading better than the older sealed ball bearing design. I see the axle flanges in the 72 rear have 1-hole, so I assume in 72 this was a standard cast axle. The only higher numerical gear ratio offered in 72 A-body 10-bolts was 3.55. In 71, 4-pinion case 3.90 & 4.33 was also offered so I assume they are heavy duty and forged. So I have 3-questions 1) are my 72 1-hole axles cast and too weak for street abuse 2) are the 71 4-pinion case axles forged and is the bearing design between 71-72 the same allowing them to be used for a 72 rear and 3) would I be better off to just put a new Auburn HP series cone posi (I believe the Pro series with more preload would be a bit more aggressive and wear out quicker on the street) in the 67 and ignore the advantages of a better bearing design for a street driven weekend toy. I know I can buy aftermarket forged axles, but I'd like to get these answers first. Tx

93Octane
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Re: Forged vs. Cast Axle Identification (BOP 8.2)

Postby 93Octane » Sun Oct 14, 2018 7:52 am

Also, will mention I'm not running a stock 71 400, but have the 69 RA D-port heads, RA exhaust manifolds, mild cam upgrade...etc, bringing HP back to the 350-370 range. Trans is Autogear case M20.

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monzaz
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Re: Forged vs. Cast Axle Identification (BOP 8.2)

Postby monzaz » Sun Oct 21, 2018 12:10 pm

Sorry been racing at the last Big Sportsman race here in Northern Ohio... Will try to get some answers.

All the Hardened axles we have pulled have the single retaining plate whole no multiply hole flange. they are in the Nodular housings and had very heavy tapered spline ends...
Castings were also rough. ..

Axles seemed to get more attention when the rears went to the Oiled bearing axles for GM Set9 or A9 bearing systems instead of the sealed bearing axles in the early cars 1964-1969
1969 LATE and through to 1972 were all the same length and bearing system. The 1973-1976 BOP A-body cars even used these same axles (slightly longer at 30" ) were used for the era. Then most all cars went to c-clip axles normal associated with Chevy cars .

Jim J D Race
J D Race

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monzaz
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Cone LSD units

Postby monzaz » Sun Oct 21, 2018 12:19 pm

We can re-machine cone limited slip differentials ONCE... after once there is just not a sufficient enough metal left to make it reliable anymore.
normally it i s in the 150.00 dollar range. We many of these for guys that want ORIGINAL show parts car restorations...
We have done many for guys drag racing also and have said it works better now than it ever did..???

4 pinion spider gear unit will be stronger than the 2 pinion spider gear unit which 2 versions also with small cross pinion single shaft 64 65 66 and larger cross pinion single shaft. 68-72

all these factory units have 2 piece side gear and cones system and needs carefully attention to axle shaft length to housing width ...IF you use too short an axle shaft in a wider housing in a limited slip factory rear NOS unit there is a chance the spline will not fully engage both pieces cone spline and side gear spline causing the unit to fail quickly under normal driving applications.

J D
J D Race

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monzaz
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Re: Forged vs. Cast Axle Identification (BOP 8.2)

Postby monzaz » Sun Oct 21, 2018 12:21 pm

ID ind forged and or cast axles.

Will have to do more home work on that... by the time we get most rears for reconditioning they NEED axles and rarely get reused again. :(

45 + years of punishment just is not good, and also the car sitting on the axles in back yards and wrecking yards tossing cars and shoving them make them rarely good for reuse.

J D
J D Race


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