[HJones1313]

My car was supposed to have a 3.55 posi, which was long gone when I got the car, replaced by a 10-bolt 3:55 one legger. My question is, if I replace the carrier with a good posi unit, add new axles and bearings, and replace the cover with a girdle-style one, is there anything else that would strengthen the rear end? By replacing these parts, I'm thinking it should be strong enough to handle 475-500HP. It's a 4-speed car, I intend to add a GV O/D over the winter, and I've already done a rear disc swap.

[ponyakr]

Assuming it's an 8.2, I wouldn't try it. With that much power, if the tires ever actually hook, it could easily break the pinion. I broke one in a '68 Bird bracket car, with a '70 455/TH400/stock 13" converter, launching from an 800rpm idle.

Some people claim they've run 10's with 'em, for years, without any problems. It's sorta like building a 557 block for 400hp. It works for some, but not for others.

My 1st choice would be a GOOD 12-bolt, with bolt-in axles. Moser builds some good ones, complete with either drum or disk brakes. But they are over $3k.

http://www.moserengineering.com/comp...musclepak.html

http://americanpowertrain.com/i-2091...body-cars.html

Other builds are available for less than the Moser price.

http://www.rearsgears.com/used-rebui...-posi-rearend/

http://www.ebay.com/itm/CHEVELLE-CUS...IAAOxye3BRr9~-

Next choice would be an Olds or Buick 8.5, which had bolt-in axles, instead of c-clips. But I think those are very hard to find nowadays.

Next choice would be a reg 12-bolt, with c-clip axles. These pop up occasionally for $1000-$1500 or so.

http://www.ebay.com/itm/CHEVELLE-12-...-/302063684553

But, a very popular option nowadays is a 9" Ford rear end. Lots of places sell these, complete, or less chunk.

http://www.quickperformance.com/GM-A...end_c_537.html

http://www.ebay.com/itm/9-Inch-Ford-...-/370267475163

[HJones1313]

You've given me a lot to think about Ponyakr. The Moser thing is out ($3k), and the only thing I forgot to say is that the car will probably never see 1/4 mile, I didn't build it for that, more for Pro Solo and (one day) the Silver State Classic closed course. A posi and axles runs about $700. I do see 12-bolts go for $400 (open) to about $800-$1000 for a posi, and I think my rear disc setup would bolt right in. I guess if I could find a used 12- bolt posi I could possibly skip the axles. I'll check out all the links you posted and become better informed.

Thanks!

STOP THE PRESS! I just found a 12-bolt on CL for $150. It's a '68 Cutlass, open, 2.78-geared diff, that would be prime for a rebuild. I don't have the funds right now, but it's encouraging to see that they're out there.

[ponyakr]

"...STOP THE PRESS! I just found a 12-bolt on CL for $150. It's a '68 Cutlass, open, 2.78-geared diff, that would be prime for a rebuild. I don't have the funds right now, but it's encouraging to see that they're out there..."


Some of those Olds rears were weird. Seems that some had a 12-bolt cover, but 10-bolt guts. That may be why it's co cheap. Nobody that I know would sell a GOOD real 12-bolt that cheap. That's what we paid for 'em back in the '70's.

"...The Type O (Oldsmobile) 12-bolt rear ends use a smaller ring gear than the Type C (Chevy) 12-bolt, resulting in lower strength. The good news it that the Type O units retain the axle shafts at their outboard ends, while the Type C units use the infamous c-clips at the imboard end. This is why you see C-Clip Eliminator kits available for the Chevy axles. Also the Chevy rear has a "scalloped" cover where the Olds is smooth.

N-bolt Differences
An Olds 12 bolt rear end is not a "true" 12-bolt. It may have 12 bolts on the outside cover, but it is a 10 bolt gear on the inside. The more common type "C" is very much different than the type "O".

A "true 12-bolt" has come to mean a Chevy c-clip 12-bolt rear. Oldsmobile 12 bolt rear ends differ from Chevys internally. In other words, the guts of a Chevy rear end will not fit in an Olds rear end housing, and vice versa. The phrase, "more like a 10-bolt", is usually talking about the size of the ring gear and/or strength of the carrier. The guts of a 10 bolt would not work or fit in a 12 bolt, and vice versa. There are differences between the 10 bolt and the 12 bolt both internally and externally..."

[rohrt]

IMO based on what you have said you can either go cheap or go strong. You will just be sweating the risk factor depending on what option you go with.

[floffy]

When you rebuild it put the moser 7900 large bearing ends on it.
I rebuild mine 8.5 10 bolt and it holds about 550hp 750 tq
Eaton 30 spline lsd moser axles and large bearing ends and a trans am cover.

['ol Pinion head]

Originally Posted by HJones1313

You've given me a lot to think about Ponyakr. The Moser thing is out ($3k), and the only thing I forgot to say is that the car will probably never see 1/4 mile, I didn't build it for that, more for Pro Solo and (one day) the Silver State Classic closed course. A posi and axles runs about $700. I do see 12-bolts go for $400 (open) to about $800-$1000 for a posi, and I think my rear disc setup would bolt right in. I guess if I could find a used 12- bolt posi I could possibly skip the axles. I'll check out all the links you posted and become better informed.

Thanks!

STOP THE PRESS! I just found a 12-bolt on CL for $150. It's a '68 Cutlass, open, 2.78-geared diff, that would be prime for a rebuild. I don't have the funds right now, but it's encouraging to see that they're out there.

At the power level you are speaking of (think peak torque), and considering the car will be subjecting the tires to a lot of side loading forces (pro solo), the absolute most affordable & strongest rearend you could have built would NOT be any form of 12 bolt, & it definitely wouldn't be the result of throwing bundles of hard earned money (just dumb) @ any gray iron 8.2 Pontiac rear. That opinion comes from a TON of experience building GM muscle rears. Best option would be an A10 housing end 8.5 A-body housing, built with 30 spline TruTrac, new Moser axles, Quality (not a $100 Chinese ring & pinion), along with Timken bearings. The larger tapered axle bearings, along with strong pinion support of this rearend make it a natural choice.

[First Bird]

X2 on what 'ol Pinion head said. This combo of 8.5, TruTrac, Moser axles, etc is holding up well behind a strong 455.

[HJones1313]

Originally Posted by 'ol Pinion head

At the power level you are speaking of (think peak torque), and considering the car will be subjecting the tires to a lot of side loading forces (pro solo), the absolute most affordable & strongest rearend you could have built would NOT be any form of 12 bolt, & it definitely wouldn't be the result of throwing bundles of hard earned money (just dumb) @ any gray iron 8.2 Pontiac rear. That opinion comes from a TON of experience building GM muscle rears. Best option would be an A10 housing end 8.5 A-body housing, built with 30 spline TruTrac, new Moser axles, Quality (not a $100 Chinese ring & pinion), along with Timken bearings. The larger tapered axle bearings, along with strong pinion support of this rearend make it a natural choice.

Thanks for the recommendation. I didn't think that was a viable option, and I'm guessing that the overall cost may be an advantage over a 12-bolt as well.

[HJones1313]

Originally Posted by First Bird

X2 on what 'ol Pinion head said. This combo of 8.5, TruTrac, Moser axles, etc is holding up well behind a strong 455.

What you and 'ol Pinion head said too!!

[TheCirque]

So is an A-10 housing a junk yard item these days or is someone putting them tgthr? And if so, is this really that much more cost effective over other options?

[vidguy]

What exactly is the "A-10" housing?

[AG]

It's a 71-71 Buick or Olds 8.5" A body rear with tube ends that accept the A10 tapered bearings. The benefit is good aftermarket support, bolt in tapered bearing axles, and the axles are pretty beefy.

[ponyakr]

If a few '71-'72 Buick & Olds models are the only source for these, I assume that they are very rare & expensive today ?

Anybody have one for sale, for a reasonable price ???

Or, would a ready-to-bolt-in 9" Ford be a better value than a correctly built A10 8.5 ?

http://www.quickperformance.com/GM-A...end_c_537.html

[abefromen]

Originally Posted by ponyakr

Anybody have one for sale, for a reasonable price ???

I've been searching CL and such for several months for one with zero luck. Found one but the guy wanted stupid money for it.

['ol Pinion head]

Originally Posted by AG

It's a 71-71 Buick or Olds 8.5" A body rear with tube ends that accept the A10 tapered bearings. The benefit is good aftermarket support, bolt in tapered bearing axles, and the axles are pretty beefy.

Yep, and due to declining amt of cores all over the country, the A10 end 8.5 A body hsgs aren't $50-150 cheap, but neither are the more common A9 hsg end '71-72 8.5 A body rears.

On the A10 end housings, have always charged out more when using that particular hsg in a build. not necessarily, because it's not the easiast to find hsg, but because stock with the larger tapered bearing, the hsg allows for a thicker axle. Typically, have used this hsg for builds for foot braked street/strip Abodys running down into the high to mid 10's. Since the bugs got worked out in the TruTracs, have sourced a few for builds, as the TruTrac is an excellent choice for hard cornering vehicle, otherwise build with a HD clutch type carrier or a spool. Have also built a few early A body width 8.5 Abody rears using donor A10 hsg ends.

[HWYSTR455]

Moser is the way to go, especially if you plan to keep the car.

You have brakes, so you don't need one of the sha-bang 'muscle-pak' rears, you just need a housing/axle package, or a housing package with guts. You can save money by having some work done locally or by yourself, or skipping some options. You can also buy it in stages, like housing, then axles, then guts, and assembling yourself, or have it done locally.

http://www.moserengineering.com/hous...-housings.html

You do want some options though if you're going to do that. Like the hybrid bolt in ends that use large bearings (think you get those if you choose bolt in axles no charge), have it shortened like 3/4" (or more) per side (rotor thickness and/or wider wheels/tires), 1350 yoke, and the axle flanges cut down to clear disc brake hats.

The housings are super strong, new units (Moser design), way stronger than any original 12 bolt. They are true, which is a SERIOUS issue when buying used, not to mention the tube walls are not as thick, welds aren't as good, and the brackets aren't beefed up. Plus, the housings are centered, which is not the case from the factory for some body styles.

I grenaded a bunch of rears in my time and finally bit the bullet (both cars), wish I would have done so earlier, I would have saved a ton of money and headache. As painful as the cost may be, if you can somehow squeeze it, you won't be disappointed in the long run.

I have a built A-9 in the 442, Moser axles, TruTrac, 3.42s, studded caps, 1350 yoke, support cover, pretty much the works, and it's a nice rear. But I have like $1600-$1800 in it. Another $1k and it would have been bullet proof. Once you do one you never have to worry about it, for a long time. I wish now I would have done it, and will probably replace it in the next few years.

And TruTracs are the smoothest application of power around corners I've ever felt, by the way. And I've driven just about every kind of posi.

.

[HJones1313]

Originally Posted by HWYSTR455

Moser is the way to go, especially if you plan to keep the car.

You have brakes, so you don't need one of the sha-bang 'muscle-pak' rears, you just need a housing/axle package, or a housing package with guts. You can save money by having some work done locally or by yourself, or skipping some options. You can also buy it in stages, like housing, then axles, then guts, and assembling yourself, or have it done locally.

http://www.moserengineering.com/hous...-housings.html

You do want some options though if you're going to do that. Like the hybrid bolt in ends that use large bearings (think you get those if you choose bolt in axles no charge), have it shortened like 3/4" (or more) per side (rotor thickness and/or wider wheels/tires), 1350 yoke, and the axle flanges cut down to clear disc brake hats.

The housings are super strong, new units (Moser design), way stronger than any original 12 bolt. They are true, which is a SERIOUS issue when buying used, not to mention the tube walls are not as thick, welds aren't as good, and the brackets aren't beefed up. Plus, the housings are centered, which is not the case from the factory for some body styles.

I grenaded a bunch of rears in my time and finally bit the bullet (both cars), wish I would have done so earlier, I would have saved a ton of money and headache. As painful as the cost may be, if you can somehow squeeze it, you won't be disappointed in the long run.

I have a built A-9 in the 442, Moser axles, TruTrac, 3.42s, studded caps, 1350 yoke, support cover, pretty much the works, and it's a nice rear. But I have like $1600-$1800 in it. Another $1k and it would have been bullet proof. Once you do one you never have to worry about it, for a long time. I wish now I would have done it, and will probably replace it in the next few years.

And TruTracs are the smoothest application of power around corners I've ever felt, by the way. And I've driven just about every kind of posi.

.

I have a lot of info to sift through, try to figure out if I look for a used one used and build it, buy one already done and be careful with the options
or just go all-out when funds allow.

[HWYSTR455]

I don't feel there's enough of a savings to warrant buying a used housing and building it, you still run the risk of the housing being bent or damaged in a way that's not immediately apparent. Plus there's still considerable work that needs to be done to the housing, further widening the gap of savings, like washing, bracket bracing, housing end replacement, tube welding, etc.

As easy as a rear is to setup IMO, so many local shops still screw it up. Most fail to check housings right off the bat for straightness, or even have a jig to do so. Same with replacing ends, most just cut the housing square to it's length and slap on the end. People end up with vibrations, or eat axle/carrier bearings, and wonder what the problem it.

12-bolts generally were installed in performance cars, further increasing the chance that they were beaten and are damaged. I just think that if you're spending the money to build out a rear, it's just better to start with a known good foundation. Sucks going through the trouble, spending the money, and later find out there's a problem with the housing. Who knows if the donor car was General-Lee'd and how many times it pancaked the pavement after flying.

If you do it in stages, the price sting is easier to choke down. Buy a carrier. Buy a ring and pinion set. Buy a yoke, seals, and bearings. Buy the axles. And when it comes time to buy the housing, you don't feel it all at once. Live with whatcha got and plan for the upgrade, just like any other big-ticket item. Like I said, once you buy a virgin, beefy rear, it will last a long time, you know it's right, and you never have to worry about it.

.

[HJones1313]

Originally Posted by HWYSTR455

I don't feel there's enough of a savings to warrant buying a used housing and building it, you still run the risk of the housing being bent or damaged in a way that's not immediately apparent. Plus there's still considerable work that needs to be done to the housing, further widening the gap of savings, like washing, bracket bracing, housing end replacement, tube welding, etc.

As easy as a rear is to setup IMO, so many local shops still screw it up. Most fail to check housings right off the bat for straightness, or even have a jig to do so. Same with replacing ends, most just cut the housing square to it's length and slap on the end. People end up with vibrations, or eat axle/carrier bearings, and wonder what the problem it.

12-bolts generally were installed in performance cars, further increasing the chance that they were beaten and are damaged. I just think that if you're spending the money to build out a rear, it's just better to start with a known good foundation. Sucks going through the trouble, spending the money, and later find out there's a problem with the housing. Who knows if the donor car was General-Lee'd and how many times it pancaked the pavement after flying.

If you do it in stages, the price sting is easier to choke down. Buy a carrier. Buy a ring and pinion set. Buy a yoke, seals, and bearings. Buy the axles. And when it comes time to buy the housing, you don't feel it all at once. Live with whatcha got and plan for the upgrade, just like any other big-ticket item. Like I said, once you buy a virgin, beefy rear, it will last a long time, you know it's right, and you never have to worry about it.

.

You bring up some good points (as usual). I'm heading towards just be done with it and get a complete diff from Moser; just have to figure out what; 12, A9, A10. Wonder if my S10 rear brakes will swap onto a 12?