[Old Goat Racer]

Please refresh my memory on this rear end. Pros and cons.
A friend of a friend is looking to buy one.
I don't remember any thing good about them.
Asking for a friend.
Thanks, OGR

[BILL BOWMAN1]

I’m no expert on the type O rears, but they are 12 bolts on the cover and 10 on the 8.5 ring gear.

[Joe's Garage]

As pointed out by Bill, it's a 12-bolt cover with 10-bolt guts.

The strength is about comparable to a Pontiac 10-bolt, nowhere near the strength of a proper Chevy 12-bolt.

Value it accordingly. Don't spend 12-bolt money for it.

[steve25]

The 0 rears that where out of the Vista cruiser wagons had 10.5 or 11” inch drums if I recall right.

Great for adding stopping power, but I don’t know about the availability of shoes for these any more, so I would check into that detail also before purchasing.

PS.
Now that I think about 72 was the first year for the 11x2” brakes, previous the option was 9x2.5”.

[b-man]

Don’t buy one.

Parts are obscure and barely available.

Really not worth buying.

['ol Pinion head]

4 different housings:

-'67-69 standard 28 spline sealed axle bearing end housings
used all three model years on all single track & high ratio Anti-Spin rears,

-'70 Tapered bearing housing end w 28 spline axles. So much confusion, not even noted in the Hollander Interchange books. Has thrown off many a repair shop over the years.

-'67-68 Low Ratio Anti-Spin housing.
This special housing was required to accept the 31 spline Anti-Spin carrier with own soecific axles w larger diam sealed axle bearings. 3.42 & 3.91 Anti-Spin rears used this style housing in '68.

-'70 W27 aluminum center housing Anti-Spin rear.
A novelty piece, most were sold over the counter. Very expensive to get into!

The last two versions noted above are restoration pieces. Have had factory Anti-Spin coded versions of each style of Type "O" Olds Cutlass/442 rear.

-New TYPE "O" gear sets are expensive & not avail in every ratio.
-New replacement posi carriers are special run affairs & expensive.
-28 spline axles interchange with same style PONTIAC 8.2 axle, so do pinion flanges.
-TYPE "O" 31 spline axles can be sourced from Moser, or Supercars Unlimited

[HWYSTR455]

The '72 442 tribute born-with rear is date coded mid-'71, has bolt-in axles, 10 bolt cover/ring gear, and had I believe 10.5 drums.

I went thru it with all new perf guts, 3.42s, TrueTrac, cap studs, 1350 yoke, Dutchman axles, brace/cover, the works. It cost about $180 less than doing a Moser 12-bolt, and sorry I didn't go that route.

It was untouched when I tore it down and had sealed bearings on the axles. It was a '72 Cutlass S 350 2bbl car.

Although it has survived some serious abuse, has about 40k miles on it, but never ran slicks on it.

It confused so many people I spoke with and who saw it, it was baffling. Even though for the most part it's been good, I still kick myself for using it. IMO, run away.


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[Jay S]

Originally Posted by HWYSTR455

The '72 442 tribute born-with rear is date coded mid-'71, has bolt-in axles, 10 bolt cover/ring gear, and had I believe 10.5 drums.

I went thru it with all new perf guts, 3.42s, TrueTrac, cap studs, 1350 yoke, Dutchman axles, brace/cover, the works. It cost about $180 less than doing a Moser 12-bolt, and sorry I didn't go that route.

It was untouched when I tore it down and had sealed bearings on the axles. It was a '72 Cutlass S 350 2bbl car.

Although it has survived some serious abuse, has about 40k miles on it, but never ran slicks on it.

It confused so many people I spoke with and who saw it, it was baffling. Even though for the most part it's been good, I still kick myself for using it. IMO, run away.


.

That one has the same gears and can use the same carrier as a corporate 8.5, tons of parts for it, it is not a 12 bolt type O. It is a lot stronger than a type O. The type O has a larger 8.5? ring gear, the same pinion bearings as a 8.2. Yours the pinion bearing are the same as a 12 bolt. If you upgraded to 30 spline axles it will take similar abuse to a 12 bolt.

Nice Cutlass 442!

[HWYSTR455]

Yes, it has 30 spline axles, the true Trac for 8.5s only come in 30 spline I believe, but it didn't fit well, and there was some doctoring involved. I know it has the ears of an 8.5, but it's an oddball for sure. Shop local to me has done a number of 8.5s for me and friends but they couldn't figure out what was going on with it either. Someone along the way told me it was a 71-72 year rear only, but have no clue. It has the ears on the bottom of the case like an 8.5, but no one that looked at it said they had ever seen one like it.

Everyone told me it takes tapered bearings too but they never worked, they were sloppy as heck, was like a hair less than a 1/4" endplay in them with the tapered bearings. I had to go back to a specific sealed bearing to make it work right.

I dunno, still, for the money, I could have just spent a hair more and did a 12 bolt.


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[JSchmitz]

As noted, parts are hard to find. My car had a 12/10 bolt 3.23 rear in it when purchased in 1985. It has taken a beating with no issues. I did find and install new clutch plates and a heavy duty "S" spring. If you have one, or can get a good deal on one, they're good pieces. I believe they are quite a bit stronger than a Pontiac 8.2. The 28 spline axles would be the limiting factor I suppose. Mine has withstood many years of 4-speed thrashing. Also over 400 trips down the track with 9" slicks and 400 turbo. Still going strong. The bolt in axles are a big plus.

[Old Goat Racer]

Thanks to all. I'll pass the info.
OGR

[lust4speed]

One last story. I sold a club member a standard BOP rearend to replace the failing Olds Type "O" in his '67 GTO that someone had stuck under his car before he purchased it. That Olds rearend sat taking up space until another club member needed an Olds axle for another orphan transplant in his '65 Tempest wagon. I gave it to him with the only stipulation that it couldn't come back. Well, the axles looked the same and the spline count was the same, but the thickness of the splines on the gifted axle prevented it from sliding into the carrier. So he ended up screwed on a spec change that probably didn't improve performance or reliability. At least it was out of my garage.

[sdbob]

A friend had a small junk yard.years ago he said I got a 70 GTO in. So went to look at it. Very rusty. It had a 12 bolt. So torched it out.The cover looked strange. I heard about McKinnon axles could this be one I thought. Pull the 12 bolts, 10 bolt carrier. Nope dont want it.

[Half-Inch Stud]

....we had bought a 70GTO 3-speed stick 400 with the Type O 12-bolt POSI. Gearing was 2.56:1

Seemed original, but the prevailing opinion was 10-bolts for 400s, or Chevy 12-bolt (3.31:1) for 455s.

So maybe some GTOs has Type O from the factory?

[ZeGermanHam]

My '66 GTO had a Type-O rear axle in it when we bought it in '94. It made a bad howling noise on decel, but I drove it for years like that through high school. When tearing my car apart for restoration, I listed it for sale on the Oldsmobile forum for $500 and it got snapped up by someone right away. It was a 3.91 posi, so it had the large carrier and was sought after by Olds guys. The buyer was going to rebuild it and put it into his beautiful '66 442, and I was very happy to see it find a home back in a performance Olds rather than being melted down.

[android 211]

I think he's on this site, 'Monzazz' who rebuilds rears. He has Olds posi units made by Yukon. He's got the lesser common odd parts. He rebuilds the GM cone style rears. I have two Pontiac 10 bolts he did and they're both great however I haven't abused them with slicks or long burnouts.

[HWYSTR455]

Yes, spoke to him regarding mine, was extremely helpful.


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[indymanjoe]

JD Race i believe (monzazz) was great to deal with. rebuilt a cone type for me and it worked great.