Which one is better?

 

9 inch all the way

9 inch vs 12 bolt is like built stock tranny vs built th400. the built stock tranny will hold more than from the factory but the th400 will hold about anything you can throw at it

i've heard of built 12 bolts snapping but never a built 9 inch making 2 times the power snapping.

 

I know a 12 bolt is about $2500, How much is a 9 inch? Isent it around the same price? If so, why do people get 12 Bolts?

Also, how much HP is a 12 bolt good for?

And is there an ABS and traction control option on the 9"?

 

As for strength of the two, it will depend on what components are used in them. But for the most part if both are built with the same type of quality parts the Ford 9" has a slight advantage. Now twices as strong, thats crap. Now for a really strong rear, both a 9" and 12 bolt can't touch a Dana 60!

 

dana 60-

someone needs to but a dana 80 behind one

 

From what I have heard, you can get a 12 bolt that retains ASR and ABS, but not a 9".

 

It depends on how you define "better." It depends on where your priorities lie.

12 bolt is strong, lets you retain ABS, and transfers torque a little more efficiently than a 9" rear.

9" is stronger, but slightly less efficient and you lose ABS.

For applications requiring maximum strength, 9" is the way to go. If you want ABS, 12 bolt is better. Moser told me their 12 bolt can hold 1000 hp. I'm sure some could site instances where their car broke a Moser 12 bolt, but it doesn't seem to happen very often.

 

I dono on this one, if your streeting it and dont want a spool, then for the F cars I have to say the 12 bolt (I like the 9" better but) Eaton makes a 33 spline posi for the 12 bolt and the biggest spline posi availble fr the 9" is a 31.
Now if your willing to put a spool in then I like the 9". I dont know why....ease of changing gears, maybe tougher???
The 12 bolt is the way to go in a F body IF you want to retain the ABS(single channel, dual channel can be set up on a 9") and they seem to fit the car better, the torque arm mount is a better design on the 12 bolt.
Basicly its a trade off, I have a 9" (and retained the single channel ABS,) there is a huge aftermarket for the ford.
Its your call both should do the job untill you see the 9's

 

With the HD posi, or a spool, the 12-bolt is good for up to 950-1,000HP. Based on my experience working with a very heavy 30th SS convertible running in the 9's (not mine, unfortunately).

12-bolt is 3% more efficient than the 9-inch. Weighs a little less, unless you start talking aluminum center section for the 9-inch. 9-inch offsets the TA to the drivers side a little more, requiring a specific TA mount (Spohn has extra holes on his TA's), and the pinion shaft sits 3/4" lower than the 12-bolt (and slightly offset to the side), putting a little more stress on the u-joints. Clearance of the TA mount to the tunnel can be a problem.... minor hammer work fixes it.

I would say if you are already at the 750-800HP level and plan to go further, jump on the 9-inch. But if you don't plan to go over 800HP, or seldom take it to the track, opt for the 12-bolt.