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 Tempest / Lemans / GTOs
 Type O Axle Swap or not
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2horse
Tribal Scout

17 Posts

Posted - 24 Jun 2015 :  11:15:21 PM  Show Profile  Reply with Quote
My 65 GTO has a olds Type O axle with an open 2.78. No clue why its under there but is in perfect condition and painted up nice. Question is do I leave it in or do I swap it out. Its gonna cost about $800 to get a anti slip carrier and gears. Are these axles strong or would I be better putting that money into a 10 or 12 bolt . Wont be building monster horse power just a strong street car. Thanks

67drake
Sitting Duck

Azerbaijan
1501 Posts

Posted - 25 Jun 2015 :  07:53:01 AM  Show Profile  Reply with Quote
That's the one with the 12 bolt cover? If so they are supposed to be as strong as an 8.5 10 bolt. Cortcomp runs (or ran) one. I'm sure he'll fill you in.
Nothing wrong with a 12 bolt,but they're so expensive these days,and are no stronger than a n 8.5 if it has an upgraded carrier,which you're doing anyway.


71' GTO Original 400 M20 3.23 posi
13.95@102.1 MPH on street tires

Edited by - 67drake on 25 Jun 2015 07:59:23 AM
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2horse
Tribal Scout

17 Posts

Posted - 25 Jun 2015 :  10:23:15 AM  Show Profile  Reply with Quote
Yep thats the one. there is a company that makes a locker its called supercars unlimited. This is the only one I can find. I plan on installing 4 wheel disk at some point so I was just wondering if this axle is worth investing in. Thanks
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cortcomp
Coyote

USA
5335 Posts

Posted - 25 Jun 2015 :  2:54:26 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I ran one but only one company made gears for them, i had 3.90s on back order for like 8 months. As soon as the BO date arrived, pushed back three months, over and over.

It's as strong a rear as an 8.5. It's a cone posi setup factory, and auburn makes cone posi setups for it. The factory bearings were blah, new ones solved that. They're nice that they're not C clip axles and are positively retained, but parts are just not that common and cost more.

A standard 8.5 10 bolt is just as good, the 7.5 or 8.2 10 bolts not quite as strong. I eventually found a completely beefed up locker 8.5 with 3.90s and put under that car. It had upgraded axles and everything, had like 2k miles on it. I sold my gone through otype for like 900, which was half what i got the other 8.5 totally done for. The cone posis are ok but as they wear, you have to machine them to get more life.

If you had access to one for under 1k that was all done and new and the right ratio and posi and everything you wanted, would be worth it. If you're adding disc later, changing gears, etc then likely not so much. Things like the upper a arm brackets that are aftermarket don't fit, different ujoint, etc.

FWIW, to me, I had OD, and 3.90s were too much, 2800-3krpm on the highway. Fun around town. 3.42s-3.73s perfect. Without OD i think i'd like 3.08 to 3.23 or even 3.42s. That'd be as numerically high as i'd go.
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Redhawk44
Tribal Scout

USA
3 Posts

Posted - 08 Aug 2016 :  7:18:43 PM  Show Profile  Reply with Quote
I know its late but it may help someone down the road. I also have a 65 LeMans with an O rear end and it has 2.78 gears. When I bought the car I looked under the back bumper and thought I scored to find a car with a 12 rear end. I found out about the O rear end when I dumped the fluids and tried to find a gasket for the rear cover. One other detractor is the cover is a 12 bolt but the ring gear is a 10 bolt. Hence , strong as a 8.5 . That's really all it is. Also, its wider than a stock 65 rear end and the parts are much scarcer and pricier.
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cortcomp
Coyote

USA
5335 Posts

Posted - 09 Aug 2016 :  09:32:31 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Olds guys will still buy them to be correct for their car. I had a W72 cover on mine, and the guy was tickled to use it for his clone. I don't dislike those axles. Just 90% of them were like 2.56 and 2.78s. I do dislike guys selling them as 12 bolts deceptively to take peoples money, but that's any hobby i guess.
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67drake
Sitting Duck

Azerbaijan
1501 Posts

Posted - 09 Aug 2016 :  09:43:13 AM  Show Profile  Reply with Quote
quote:
Originally posted by Redhawk44

When I bought the car I looked under the back bumper and thought I scored to find a car with a 12 rear end.



Yup,and that's where a lot of people screw up. Like we said above,nothing wrong with the "O" rear end,but it's not a "12 bolt" (Chevy). Parts can be hard to find for the O,but an 8.5 A body from a '71- 72 Buick or Olds A body will drop right in and parts are a lot easier to find.
Edit- The '64 to '67 rear ends are a different width!


71' GTO Original 400 M20 3.23 posi
13.95@102.1 MPH on street tires

Edited by - 67drake on 09 Aug 2016 09:48:14 AM
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DanM
Buffalo

80 Posts

Posted - 21 Dec 2016 :  5:00:09 PM  Show Profile  Reply with Quote
I'm not entirely sure what the O rear end is since that's not my year. I'm familiar that there are several sizes and so I'll just go with that.

This past January I spent way too much time researching my rear end on my 71 Lemans. The stock rear end was an open 2.56. This is an open 3.23. I really loved the open 2.56 since I spend so much time driving at 80 mph on the highways. The 3.23 are just too short but they are night and day off the line.

Mine is an 8.2". 27 spline pinion and 28 spline axles. when my TH350 finally conked out I replaced it with a 200-4R. Since I had OD I then pulled out the 2.56 and rebuild my 3.23 with posi. I was not able to find 3.23 gears so I ended up with a Richmond 3.55 and an Eaton posi.

What a joy! Now I can leave two black lines, do donuts and still cruise 80 mph at 2500 rpm!!

71 LeMans Sport Convertible with 310,000 miles driven year round since 1994.
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cortcomp
Coyote

USA
5335 Posts

Posted - 21 Dec 2016 :  8:39:41 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
OD and 3.32-3.42 is just a great combo. I had OD and 3.90 for a minute and it was a bit much, but it fit the cars attitude. I have OD and 3.73s in a 56 chevy right now, it seems decent on the highway. 2500ish rpms. I think 3.42s are about just right for me.
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