12 bolt vs 9"

[Reaper]

I need to start thinking about what I want to do for real.... either beef up the 12 bolt or start building a 9"

I like the thought of a 9" just because its a lot easier to change the gears... Could use one set of gears for everyday cruising around or whatever and then another set of gears for when I want to play at the track... but its not that important to me as I will probably just run something around a 3.42 rear gear. I dont think Ill need anymore than that at the track and its not to bad on the street. Another thing with the 9" is no c-clips.... yes I could get c-clip eliminators but Ive heard that they can leak if you drive a lot on the street. I like the 12 bolt because its a GM rear and Id like to keep it... Not to mention it would save me some money on buying a 9" housing...

What all do you guys think would seriously have to be done to the 12 bolt to run 9's with a supercharged big block? Not to say that I will be running 9's but just incase I ever do try for it... A friend of mine and I are in kind of an ET race...

Would I have to do anymore than; welding the axle tubes, girdle rear end cover, after market axles (what spline do you think?), 1/2" studs, c-clip eliminators or 9" housing ends (What do you think would be best?). That is all I can think of... anything else I might have to do?

When I do put a supercharger on the 460 Im gonna be trying for about 750-800 HP.... To give you more of an idea....

Thanks, Tom

[Sam (Bones)]

 

9" hands down

[502ci]

I personally would stick with the 12 bolt, you could get it to hold up to the power you are talking about. Call Moser's tech line, they will give you alot of advice whether you go with a 12 bolt or 9 inch.

 

Here's a link...http://www.moserengineering.com/index.html

 

I talked to them back when I was seriously gonna add a F2 Pro-Charger to my 502, they said they could build me a 12 bolt to handle a 1,000 hp supercharged motor. The fact you only want 3.42 gears helps the matter all the more.

 

Also remember a 12 bolt uses less power to rotate than a 9 inch. I say keep it GM...

 

 

[Guest 72yellowmc]

I personally would stick with the 12 bolt, you could get it to hold up to the power you are talking about. Call Moser's tech line, they will give you alot of advice whether you go with a 12 bolt or 9 inch.

 

Here's a link...http://www.moserengineering.com/index.html

 

I talked to them back when I was seriously gonna add a F2 Pro-Charger to my 502, they said they could build me a 12 bolt to handle a 1,000 hp supercharged motor. The fact you only want 3.42 gears helps the matter all the more.

 

Also remember a 12 bolt uses less power to rotate than a 9 inch. I say keep it GM...

 

 

DITTO!!!!!!!!!!

[Heckeng]

I agree with Sam. . .And Bill!

 

I think the 9" is the way to go if you're serious about power and getting in the 9's-10's. With either style axle you should have the 9" style ends, not C-clip eliminators or anything like that. If you are ever going to pay for a housing though, go ahead and get the 9"

 

If you currently have a 12 bolt and want to get by for the time being, have some ford housing ends welded on, and get some larger splined axles put in it and it will be good for a lot of power.

 

Take my advice for what it's worth though (not much), I'm a guy who is still trying to make a th350 last behind a BBC!

[Reaper]

Thanks guys... I will contact moser and see what it will cost both ways and see what they think....

Thanks, Tom

[680HPStroker]

Call Tom's Axles. They can either build, or sell you the parts to build an almost indestructable rearend cheaper than the big names. If you are going to have a local shop set it up for you I'd recommend having your axle tubes welded. Stay 12 bolt. Your wallet will thank you.

[monte0]

I'd say 9" too. I've had both and the 9" is a great rear. (Given I did build it a little more then the 12 bolt)If I remember right, it cost me about the same to build the 9" completely new then it would have to build a 12 bolt to the same strength.

[Guest Rice Racing1]

[

I talked to them back when I was seriously gonna add a F2 Pro-Charger to my 502, they said they could build me a 12 bolt to handle a 1,000 hp supercharged motor. The fact you only want 3.42 gears helps the matter all the more.

 

Also remember a 12 bolt uses less power to rotate than a 9 inch. I say keep it GM...

 

Actually the higher the gear ratio the quicker you will break a ring and pinion. With a 3.42 gear the ring and pinion will carry more of the torque load than a 4.30 gear will. A 4.56 or lower gear will put more load on the axles than the ring and pinion.

 

Yes a 12 bolt uses a little less power to turn. But a 9" has an advantage in a strip application you may not realize, Due to the pinion location on the ring gear it causes the pinion to climb the ring gear causing the housing to rotate making a proper rear suspension to plant the tires harder.

That means you will get more traction and a quicker 60' time from a properly setup rear suspension with a 9", no the less power loss from a 12 bolt won't make up for it!

So a streeter can survive with a 12 bolt. A strip pounder may get by with a built 12 bolt but it will fail sooner than a 9".

A 12 bolt can be built to survive 1000 hp for a awhile true, It will not take it nearly as long as a 9" will. Even if you up grade to 33 sline axles, a detriot locker, ford axle tube ends and a girdle cap cover. the ring gear and carrier still deflect more under load than a 9" does due to the lack of the thrid pinion support bearing. Therefore the the ring and pinion wears faster and is more prone to breaking than the 9".

I have built both to the max and the 9"'s always last longer.

You can build a 9" without useing any ford parts at all, that makes it a AFTERMARKET rearend not a ford!

Don