12 bolt vs 9"

[Kal]

Hey guys,

Which rear end do you think is the best? I'm going to upgrade from my 10 bolt and was wondering if one was better than the other. Ofcoase ever body knows that the 9" is a little bit stronger but what about driveablility?

Right now i'm only going to put 350-400 horses to the ground but i eventually plan on upgrading in the future to twin turbos...would it be wise to go with a 9" right now even tho i hear the 12 bolts are more efficent?

Thanks for the help!

[Goatman]

If you're going to street drive it only, then I'd go with the 12 bolt. If you're going to race it with the TT's, then I'd go with the 9 inch.

I had a 12 bolt in my old GTO and it ran a best of 10.09 @131 weighing 3400lbs.. They can take a beating, but for constant race abuse, I'd go with the 9 inch. The one piece housing and stronger center section are worth the extra weight and HP drag. On the street, you're going to spin the tires, not hook, so the 12 bolt will work for you.

The driveability of either will be determined by your gear and posi/locker choice.

[Kal]

Thanks Goatman,

My intentions are to build a car with driveability... you know, take to car shows ect...

but, I'll still probably end up taking it to a road coarse/ drag strip once in a blue moon so i can prove it can handle as good as it looks.

What posi/locker would you recommend? I was told i should go with a Moser 12 bolt trutrac. I'm not too familar with really any other choices.

[SicMonte]

i just ordered a moser 12 bolt with the true trac center. Mine is a street car with about 420hp and it gets road raced every so often.

[big gear head]

As far as a stock rear end goes, the 12 bolt is stronger than most common 9 inch Fords. When you start to modify them then the 9 inch becomes stronger. The 12 bolt is a simpler rear end. Some of the after market 12 bolt housings are much stronger than the original 12 bolt housings, so they can be built to handle more power than any of the old 12 bolt rear ends. Then there is the Dana 60, which is probably stronger than any 12 bolt and most 9 inch Fords. The Dana is usually cheaper to build too.

[Goatman]

Kal, I'm going with the TrueTrac as well..

[ProdigyCustoms]

A 12 bolt Tru Trac 33 spline is stronger then a Tru trac 31 spline 9". and the 9" does not get stronger until you go to the dreaded 35 spline Detroit locker. We sell a lot of Moser 12 bolts for applications to 600HP

[TnBlkC230WZ]

You didn't say what year your 8.5 was. The 72 and later are nealy as strong as the 12 bolt (with 30 spline axles and 1.625 pinion) and will easily hold your 400 HP.

[ProdigyCustoms]

You didn't say what year your 8.5 was. The 72 and later are nealy as strong as the 12 bolt (with 30 spline axles and 1.625 pinion) and will easily hold your 400 HP.

This is true. We have a friend that runs low 9s on a 8.5 with a spool and performance cover in a 3500LB car

[nancejd]

I went with the 9" in my car. One thing I liked about it was that I can run a 3.70 gear set, and when I want to run power tour, or some other long distance cruise, you can swap in a different center section, and not have to reset all of your gears like you would with a 12 bolt. On the downside, the 9" will eat a little more horsepower, but they do seem to have a wider selection of gear sets.

[Motown 454]

Hi i'm putting a Chris Alston Fab 9" in my 69 Camaro I have a Bill Mitchel 454 sm blk 600 HP 575 TQ. I'm putting 35 spline axles in it, It will be mostly street driven with a Viper 6 spd and 4:10s I know very little about ford rears, what posi unit do you guys recomend? I don't want the chattering around corners like with a spool. if anything some quarter mile trips just for time slips. Thanks Wayne

[Goatman]

35 spline axles for 600hp??? Overkill and will limit your selection of posi units to lockers and spools most likely...

[ProdigyCustoms]

Motown, you need a 33 spline 12 bolt. Your only differential option that is stronger then the 33 spline 12 bolt is the clunking and banging 35 spline Detroit locker, which you DO NOT need! As mentioned above, not only over kill, but a horsepower stealer to as the 9" is less efficient, and the larger over kill heavier components take more to turn also. The 12 bolt with the Performance cover is every bit as cool looking as a fab 9

[big gear head]

Your only choice for 35 spline axles in the 9 inch is the Detroit Locker. Go with the 33 spline 12 bolt, or good 31 spline axles and a Truetrac in the 9 inch if you already have the housing.

[67RS]

Frank,

Do you have the part number for the 33 spline 12-bolt truetrac? I have the Eaton catalog and don't see it listed.

I won a free diff. at the Kalamazoo stop of the power tour and I'm pretty sure that's what I want to get. Right now my camaro has the original 8.2" 10-bolt and I don't want to bother building it up. I don't have a 12-bolt housing yet but I figured I would get the diff. and worry about the rest later.

[ProdigyCustoms]

Condratulations on winning the rear. WEaton is Eaton, Tru Trac is Detroit, hence why you cannot find a Eaton part number for a true Trac. Sorry I missed ya on Power Tour, I had to get back to the shop and could only do a few days.

[67RS]

Your right but Eaton owns Detroit Locker and Detroit Truetrac and all three are listed in their catalog but the 33 spline 12-bolt one is not there. Any ideas?

[ProdigyCustoms]

Hum? Call Rocky at Moser, tell him I suggested you call him. Tell him your situation and he mat be able to help you

[67RS]

Thanks Frank. Rocky helped me right out. If anyone cares the part number is: 914A576.

[blown71]

Had both 9 inch and 12 bolt
and True Trac and Eaton posi

My chioce 9inch and true trac