[dannla]

I ahve a 70 GTO that I am building a 472 stroker engine for. It should have between 470-500 HP and close to 600 ft torque (flywheel). I am planning on running a tko600 5-speed behind it.

I am worried that the stock 10 bolt may break and have a couple of rear ends in my parts stash to choose from. I have an original HD rear end out of a 69 GTO with a nodular housing, 4 pinion 3.90 posi, with factory forged axles. I also have a non-nodular 12 bolt out of a 70 grand prix (3.08). Both rear ends are stock, drum to drum.

I will adjust / replace the gearing as I see fit, but am wondering which of these housing would be better able to handle the torque of the engine / trans combination. Are the stock axles in the HD rear end sufficient or should they be replaced?

I would assume that the best bet would be a nodular 12 bolt out of a Pontiac, but I don't have any of those in my parts stash. I don't want to go the 9" route and I am not so sure that a 9" is that much stronger anyway.

Any input would be appreciated.

[steve25]

Even a 12 bolt non nod is stronger than the early 8.2" 10 bolt, or the later 8.5" 10 bolt, plus you have way more gear ratio`s ou can pick from.

[The Boss]

12 bolt.

['ol Pinion head]

Originally Posted by steve25

Even a 12 bolt non nod is stronger than the early 8.2" 10 bolt, or the later 8.5" 10 bolt, plus you have way more gear ratio`s ou can pick from.

The 12 bolt will be stronger than all the different gray iron 8.2 variations, BUT a 12 bolt car housing does NOT have more pinion support than an 8.5 10 bolt, pinion support plays a large point in determining housing strength.

Upgraded the factory 12 bolt posi carrier with new heat treated 10-17 side gear/spider gears, & new hd axles is a good starting point. Same can be done with an 8.5 A-body 10 bolt & if you choose housings wisely, can have a A!0 axle bearing version allowing even larger diam aftermarket axles.

[Big Injun]

Yep, upgrade the 12-bolt and install the gearing your wish. I myself would go with an Eaton Posi and 3.31 gears behind the TKO.

[Tim Corcoran]

If it's gonna be a street only car then the 10 bolt should be fine, But if you plan on putting slicks on it and doing drag racing then I would worry more about the trans than the rear end. Properly prepared 10 bolts will hold up to a certain level and of course the 12 bolt would be the best choice. A properly prepared 12 bolt will hold up to some pretty serious drag racing provided you have after market steel axles. Again for the street the 10 bolt should be fine because tire spin will keep parts inside the trans and the rear.

[GoatDr]

I'd put more gear in it for a TKO overdrive. Put 3.90's in it.

[HWYSTR455]

What Tim said, totally agree. The TKO600 is 'supposed' to be good to 600 ft lbs, but people have broke them with less. If you are going to puts slicks on it, or even street stickies, 12 bolt for sure, and aftermarket axles. Once it's time to do the trans, cryo is your friend.

Best would be a Moser 12 bolt housing. Even better would be a Moser housing with Ford big axle bearings. My driver EATS right rear axles bearings, it's a Moser 12 bolt housing, Moser axles, but OE style bearings. And that's almost strictly on the street. I've had the housing checked for straightness twice, the ends, everything, it just is at that level (and the way I drive) that beats the heck out of it.

A 9" is a great choice too, but not sure what you're thoughts are there. (more original looking or what)

You could probably sell the two you have and offset the cost of a new one. Or you will most likely be replacing either at 15 - 20k miles or so. A 472 is not your dad's Bonnie 455.

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[dannla]

Hwy. what did you mean when you siad that "cyro is my friend"...I'm sorry, I dont recognize the name / refrence.

Thanks to all that have repleid.

[mrennie]

Cryogenics, a method of cold treating parts to an extremely cold temperature which reduces stress and improves durability.

Some trans parts (gears, shafts) are treated this way to improve strength.

[Tim Corcoran]

Basically you would take your trans to a shop that does this cryogenic process and that will put your trans in a chamber and flood it with liquid nitrogen. It's kind of like heat treating but it's more like a final conditioning after heat treat. There is a thread here that talks about the process in great detail. I agree you should have this done to your trans. The TKO is the weak link in your combo.

[HWYSTR455]

Look at American Powertrain for 600 parts that are cryo'd:

http://www.highperformancepontiac.co...e/viewall.html

Pretty good article too....

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