[Targa]

I know this is obvious.. the Ford wins hands down strength wise.

But, issue here is I have a 12 bolt in my 2nd gen bird now so its paid for.

Is it worth the cost to upgrade it to the 9 inch strength (if this is even possible with a 12 bolt) or should I just sell the 12 bolt and get into a 9 inch?


Plus, I was pretty sure I was going to add this torque arm suspension to the rear end of my car next month. It uses your existing 12 bolt housing....
http://www.bmrfabrication.com/index....&productid=533


In the 9 inch version, they provide the housing but it costs you 500 bucks more since the suspension is built onto this housing, not just bolted on.
http://www.bmrfabrication.com/index....&productid=535

Will be adding their front upper/lower control arms as well.

Anyone care to chime in here?

Does anyone here have or know of anyone who has used this suspension before?

Good? Bad??

Will be running a 520ci turbo motor @ projected 1000hp on the street though. Not strip.

In mid Nov. this Co. usually has a Veteran's sale with 15% off and an additional 10% off if you are active in the military. At least last year that was the sale. This year the guy was not sure what it was going to be, but said there will be something going on.

TIA for any insight.

[Jack Gifford]

I can't answer all of your questions. I believe that a torque-arm arrangement is a wise choice for a street or road race machine. But for dragstrip use, however, I feel that it would lack adjustability. To change the instant center of rear axle movement appreciably would require considerable change to the arm's effective length. Such an arm could be designed, but I haven't seen one being marketed.

[ponjohn]

With that type of power on tap I would consider a Strange 60.

With any type of hard launch the 12 bolt will give it up especially if you run a posi vs a spool.

What does the car weigh?

[Targa]

John,

Its a full weight 2nd gen bird. Nothing removed. Same weight as new in 77 I am guessing and then some actually. so what.. 4,000lbs...lmao.

It is a manual trans car too. No auto here...

Thanks.

[67copperbird]

If you are doing nothing but street driving I would stick to the 12 bolt. The extra $500 only gets you the 9 inch housing. This doesn't include axles or center section? Take you $500 and send the housing to someone and have them add Torino ends and set you up with a new wavetrac 35 spline set-up (you can get a whole 12 bolt with this set-up for around $2900 or so). I am assuming since you said street that you are running some sort or street or road race tire? I can tell you with that much power and street tires that u-joints and tires will give faster than what the 12 bolt will.

[67cruiser]

I was recantly told by a machine shop it takes 12 to 15 hp more to run a Ford 9 inch than a 12 bolt chevy???Just what i was told!!

[455HOUK]

I'd be interested to know what manual trans and clutch you are intending to use with that much power?

[Tom McQueen]

My 70 GTO will weigh 3500# and the procharged 555 should make close to 1100HP.

Im using a McLeod dual disc clutch, a worked over T-56 (same manual used by the twin turbo Viper guys) and a Mark Williams 9" rearend.

Ill still break stuff. Its inevitable at these power levels.

[HWYSTR455]

Originally Posted by Tom McQueen

Ill still break stuff. Its inevitable at these power levels.

Not if it doesn't hook! Or at least that's what I'm counting on!

I've been back and forth on the 12 / 9 issue, and finally just went 9, for a number of reasons. But then again, the waveloc wasn't available at the time either. Between the two, it's pretty much a toss-up, really. (Especially if you're not having to change rear gears for different tracks).


.

[Targa]

Trans I was looking at a Tremec.

Stock T-56 for any Viper at 03 and up is only good for 550ft lbs of Tq. so that was out.

Or you can upgrade it to a stronger unit as well. But, then it gets expensive (for street) to get a bell setup, speedo and pedal assembly. I looked into this originally.

The trans I will be worrying about last since I have a bunch of different 4 speeds laying around.

Probably run the ST-10 for the initial drive time. Wont be going crazy with it since it will self destruct...lol.


Anyway, the real problem here is I can not seem to locate anyone spec'ing their 9 inch parts for hp/Tq. rating same with a 12 bolt.

Yeah, I understand that there are so many ratios available and that will make a difference but hey.. there has to be some guide line for reference.. no?

[HWYSTR455]

Yes, there is, though my initial searches aren't coming up with anything. Couple things I do know is this:

Axles were a determining factor when rating housing from the factory. Replacing those make a very large jump in torque capacity, especially if going to like a 40 spline.

The center section case makes for another area to increase strength, first jump is to the nodular, then custom aftermarket ones after that (for the most part).

Center section pinion support types, the 'Daytona' style being the common upgrade, though there are larger (in custom cases).

Housings also play a part, stamped, stamped with long 'ears', fabricated, and believe there's even cast. Tube thickness & diameter is also part of that, keep in mind.

Differentials too, play a part, custom spools making the top of the chain.

Hardware, center section studs, wheel studs, etc, all play a part, if you get particular about it.

One overlooked area of strength is ring and pinion gears. Certain ratios, the ring gear gets thinner, effecting overall strength.

So, it's tough to gauge the strength by just saying a '9 inch', too many factors. The big guys in like pro-mod are still using 9" rears, and those guys are laying down some power. What, maybe in the 4000hp + range? Gives you an idea. If you really want more specific info, I suggest calling like Moser or Williams.

As for manual transmissions, yeah, the 600-700 ftlbs range is pretty much the limit for 'generic' stuff, and the high end stuff is high dollar! Look at the Liberty, G Force, or like transmissions. They run upward of like 7k. Not sure how much the transzilla t-56s are, guess you could call. They're rated at 1000 ftlbs.

.

[Ron]

There are 9 inch housings and then there are 9 inch housing. The OEM style of 9 inch is stronger than a 12 bolt. Why...because of two things. The ring gear of the 9 inch is larger than the 12 bolt and the intersection of the ring and pinion is lower in the ring on the 9 inch. This provides a better tooth contact area.

Now...housings. OEM housings do not have any reinforcement in them and the tubes are thinner. After market housings such as FAB 9, etc are much beefier and will handle lots and lots of torque. For instance. The flange where the center section bolts into the housing on an after market housing such as the FAB 9 is thicker.

My car is not near as heavy as a modified street/strip car. With me in it it weighs 2770...ready to race. Plus I'm a tube chassis car. However I do make around 875 pounds or torque at 4900 RPM. I have the FAB 9 and run 35 spline axels without issues.

[BruceWilkie]

Originally Posted by ponjohn

With that type of power on tap I would consider a Strange 60.

With any type of hard launch the 12 bolt will give it up especially if you run a posi vs a spool.

What does the car weigh?

If I were him I would at least call Strange. They do 12 bolts 9 inch and the Dana 60. My guess they will suggest Dana60 type unless you need lower numeric gear than 3.54. Stock Dana60 comes with 35 spline axles. S60 is @15lbs heavier than a 12bolt. WAY stonger.

[andrewT]

Only rear end I would ever run in a manual car that makes power is a Dana 60. I think although 9 inches are the "industry standard" they are overrated imo. I wouldn't bother going 9 inch, the 12 bolt isn't much weaker.

[goquick]

Between a 9" or 12 bolt junk, 9" WINS EVERYTIME!!! I have broken quite a few 12 bolts over the years. Even with all the "good" stuff avalable for them! By the time you buy enough aftermarket parts to keep a 12 bolt toggether for a few good hooks, you could have had a fab 9 type rear with a MW 10 5/8" ring gear.

[Tom Vaught]

Originally Posted by Ron

There are 9 inch housings and then there are 9 inch housing. The OEM style of 9 inch is stronger than a 12 bolt. Why...because of two things. The ring gear of the 9 inch is larger than the 12 bolt and the intersection of the ring and pinion is lower in the ring on the 9 inch. This provides a better tooth contact area.

Another thing about the 9" Ford Axle is that the Pinion (as in Ring and Pinion) is SUPPORTED behind the Ring Gear whereas the 12 bolt has NO SUPPORT in that area.

99% of all Chevrolet "Super Street" class racers are running 9" Ford Housings or Dana Housings. Most of the guys are also running trans brakes and converters.

The DANA is KING when it comes to handling shock loads from a Manual Transmission.
You will kill the trans, any street transmission, before you will hurt the DANA.

Tom Vaught

[Ron]

Forgot about that Tom.....thanks for the reminder.

[Probird]

If you aren't racing it the 12 bolt will be fine. I run a 12 bolt in my car with 33 spline axles and a spool. Car weighs 3200 and has been 1.29 60' with a transbrake - mid 9's in the 1/4. The same rear has been in the car since I bought it 18 years ago, minus a few gear sets. It probably has 3000 passes or so and is holding up fine.

[Stormin]

Now that is good to hear!
I'm in the midst of building a tube chassis "pro street" car...and because of spending too much in other places.. I am planning on running my street/strip motor and the 12 bolt that was in there before.
My chassis shop is begging me to convert to the 9 inch.. but.. dollars and cents right now make me stay with the 12 bolt.

The other thing that makes me stay with the 12 bolt is...that rear has strange axles and gears and a moroso posi case.. and when the car weighed about 3,400 lbs.. it has made numerous 10 sec passes and never a problem with the rear or anything associated..oh.. one problem.. just a u joint. probably from some of the street driving that was done.. and there was a lot of miles put on it on the street.

So.. as much as I would like to switch to the 9 inch.. I'm comfortable for now staying with my 12 bolt.. until a later date.. for when my "race" motor goes in.

All great advice to consider though guys.
It's appreciated
take care
NB

[Half-Inch Stud]

I gots the Strange Dana60 in the 68GTO; is super butt it can only get to 3.54:1. No worrys. Perhaps it is the most Economical down to 8's?

I hads the spooled 12-bolt go 1.50 60foots for 11.0:1 using Strange Axles...and was only concerned.
I hads the posi 12-bolt go 1.60 60foots for 12.0:1 using stock GM Axles...and was scared each time.
================================================== =============
Upon careful review of the 9" FORD rear, I'm riddled with concerns when using factory parts. When the aftermarket housing is stuffed with aftermarket parts I'm only concerned with COST, and the looks of a sheetmetal FORD housing in me GM machine. HIS