Best choice- Corporate 10 bolt or O?

ziff396 · August 2nd, 2008, 06:08 AM

What are the pro's and cons of each? I have a 72 corporate open with 2.73's and also a O rear with 2.56 gears out of a 70. Both are out of Cutlass's.
Which would be the best choice to rebuild and convert to posi units with 3.42 gears? I'll be running a strong street 455 with a turbo 400 trans.
Thanks for any help!
Kevin

72 Cutlass in progress.

BILL DEMMER · August 2nd, 2008, 10:01 AM

from what i've always heard, the availability of parts for the O are poor.
i know the guy that did mine thought more highly of the corporate r.e. and had some difficulty locating the parts for my O r.e. but, he got it done on time and under budget.

bill

joe_padavano · August 2nd, 2008, 11:15 AM

Strenght-wise they are pretty much equivalent. Both use an 8.5" ring gear with ten bolts. The parts availability pushes the corporate axle to the top.

BILL DEMMER · August 3rd, 2008, 12:27 AM

joe,
i thought the type-o was 8.2" and only used 10 bolts on the ring gear to carrier vs. the corporate 12 bolt with an 8.5" and 12 bolts for the ring gear to carrier.

bill

Run to Rund · August 3rd, 2008, 08:59 AM

Thre were type B and P 8.2s used in 64-7. Type O was 8.5, ten 7/16 left hand threads (iirc) on the ring, 12 bolt cover, from May 66-70; thru 68 with 31 spline, 69-70 with 28 spline axles. Corp 8.5 was mostly 71-2 in terms of mounts for 64-72 A bodies, with 10 cover and ring gear bolts.

For best strength, the corp 8.5 has the most stuff available, as noted above. Many weld the tubes to the center section with nickel rod, but it should be done by someone good and carefully to avoid drawing the tubes out of alignment.

I did a cost comparison a couple years ago with the 8.5, 12 bolt Type C, and Type F ten bolt (9" Ford). Mild builds--you can save if you already have something to start with. Full builds, pretty much the same cost for all of them.

joe_padavano · August 3rd, 2008, 01:00 PM

Quote:

Originally Posted by BILL DEMMER

joe,
i thought the type-o was 8.2" and only used 10 bolts on the ring gear to carrier vs. the corporate 12 bolt with an 8.5" and 12 bolts for the ring gear to carrier.

bill

Bill,

The 8.2 is the earlier axle. The 67-70 Type O is 8.5", 10 bolt ring gear. The Corporate 8.5 is also ten bolts on the ring gear. The Chevy 12 bolt is an 8.875" ring gear with 12 bolts.

August 2nd, 2008, 06:08 AM	#1 (permalink)
ziff396 Registered User Join Date: Jun 2008 Location: Michigan Posts: 63	Best choice- Corporate 10 bolt or O? What are the pro's and cons of each? I have a 72 corporate open with 2.73's and also a O rear with 2.56 gears out of a 70. Both are out of Cutlass's. Which would be the best choice to rebuild and convert to posi units with 3.42 gears? I'll be running a strong street 455 with a turbo 400 trans. Thanks for any help! Kevin 72 Cutlass in progress.

August 2nd, 2008, 10:01 AM	#2 (permalink)
BILL DEMMER Just the facts... Join Date: May 2008 Location: THE GREAT WIDE-OPEN Posts: 208	from what i've always heard, the availability of parts for the O are poor. i know the guy that did mine thought more highly of the corporate r.e. and had some difficulty locating the parts for my O r.e. but, he got it done on time and under budget. bill __________________ '67 CUTLASS 4-DR. W/425 & S.P. THM400 (NAMED "ERNIE") '83 H/O #1339(STILL IN PIECES) '85 PONTIAC FIERO SE V-6 4-SPD. BOUGHT NEW '92 CHEBBY DIS-ASTRO (GAS PIG) '97 GYRO METRO $HYTBOX (41.42 MPG)

August 2nd, 2008, 11:15 AM	#3 (permalink)
joe_padavano Super Moderator Join Date: Mar 2007 Location: Northern VA Posts: 4,398	Strenght-wise they are pretty much equivalent. Both use an 8.5" ring gear with ten bolts. The parts availability pushes the corporate axle to the top. __________________ Joe Padavano 64 Jetstar 88 Conv 66 442 L-69 Conv 68 W-30 69 H/O 69 442 70 W-30 72 442 84 Custom Cruiser 86 Caprice wagon (w/307 Olds)

August 3rd, 2008, 12:27 AM	#4 (permalink)
BILL DEMMER Just the facts... Join Date: May 2008 Location: THE GREAT WIDE-OPEN Posts: 208	joe, i thought the type-o was 8.2" and only used 10 bolts on the ring gear to carrier vs. the corporate 12 bolt with an 8.5" and 12 bolts for the ring gear to carrier. bill __________________ '67 CUTLASS 4-DR. W/425 & S.P. THM400 (NAMED "ERNIE") '83 H/O #1339(STILL IN PIECES) '85 PONTIAC FIERO SE V-6 4-SPD. BOUGHT NEW '92 CHEBBY DIS-ASTRO (GAS PIG) '97 GYRO METRO $HYTBOX (41.42 MPG)

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August 3rd, 2008, 08:59 AM	#5 (permalink)
Run to Rund Registered User Join Date: Mar 2008 Posts: 339	Thre were type B and P 8.2s used in 64-7. Type O was 8.5, ten 7/16 left hand threads (iirc) on the ring, 12 bolt cover, from May 66-70; thru 68 with 31 spline, 69-70 with 28 spline axles. Corp 8.5 was mostly 71-2 in terms of mounts for 64-72 A bodies, with 10 cover and ring gear bolts. For best strength, the corp 8.5 has the most stuff available, as noted above. Many weld the tubes to the center section with nickel rod, but it should be done by someone good and carefully to avoid drawing the tubes out of alignment. I did a cost comparison a couple years ago with the 8.5, 12 bolt Type C, and Type F ten bolt (9" Ford). Mild builds--you can save if you already have something to start with. Full builds, pretty much the same cost for all of them.

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