Why a 9" over a 12 bolt?
 

Why does everyone seem to want to buy a new 9" for their GM cars when you can purchase a new 12 bolt? Unless you are looking to change gearsets in a hurry, a 12 bolt will hold up fine for what the majority of people will be using their Pro-touring cars for. Do people feel the 12 bolt will not hold up or do they actually like the appearence of a 9" under their GM car. I AM NOT KNOCKING FORD IN ANY WAY SHAPE OR FORM!! I want to make that clear, I like all American muscle cars wether they are GM ,FORD or CHRYSLER. I would like to hear what people think. Most peolple I know choose to stay with a 12 bolt in their GM car. When I look at all these awsome cars I notice a lot of people choose a 9" and always wonder why. Thanks

its preference I guess......one benefit that comes to find is no c clips or c clip eliminators on a 9in. THe gear sets are bigger and stronger. No cover on the rear allows the use of a rear axle back brace. Im sure there are more but its early and i can't think right now. :_paranoid

When buying new
 

Most of these guys seem to be buying new. You can buy a new 12 bolt from Moser with ford housing ends. You now have no c-clips. Check out www.rhodescustomauto.com and check out the two camaros on the home page, 1 red and the other blue. Both run 12 bolts without a problem. If you want to see more of the car go to finished cars and you will see more photos of the car. And they look better. I have been friends with Ron (red Camaro) since we were kids. That 12 bolt has been in his car forever. Can anyone agree that a 12 bolt looks perfect under a camaro instead of a 9 inch, or I am just being a bit anal about it? Speaking of Rhodes Custom Auto. If anyone needs any work and lives near Delware, Ron and his father Larry do incredible work. They have been building street rods, custom street cars and race cars for 30 plus years. They build a lot of show cars also. Starting to sound like an advertisement so I will end it now. Thanks Dave

I have been wondering same too. Does GM rear have pinion in more favorable postion than 9" ? Steve reported at he had some wheel hop with 9" but not with 12 bolt?

What about the weight differences?

yes you can custom order the rear end with 9in ends. A 12 bolt takes less power to turn but they will not hold as much power as a 9 in due to where the pinion rides on the ring gear I think...I am not a rear end guru though.

the 9" has an extra bearing/support on the snout of the pinion, making for a stronger interface between the ring & Pinion, and a larger diameter ring gear. more aftermarket parts BY FAR, easily weldable formed plate steel center section, opposed to the cast center of a 12 bolt. easy gear changes, cheaper LSD's, etc. blow up a 9" third on a road trip, slap another one in from a junkyard, blow up a 12 bolt on a road trip, find a new rear. :unibrow:

9 inch
 

Yes 9 inch rears have many advantages when it comes to the things that have been referred to. Who uses their pro touring car in such a manner that the likleyhood of blowing it up is really there? Are these pro touring cars yanking the wheels of the ground in 1/4 mile drag racing? Check out www.rhodescustomauto.com and that camaro has a 1.3 60' time with a 12 bolt. Does anyone with their street cars stress their rears more than that? If your car blows the rear on a road trip who is actually going to do the that kind of work on the side of the road or in a parking lot? I don't know anyone who would. It would be trailered back home no matter what kind of rear blew up. Besides, how many people with 9" rears in their street car actually have a spare center section already set up and ready to install in the event a rear blows up on a road trip.

sounds like you have your mind made up.

Well, since we have been selling the crap out of Moser rears, I have learned a bit about rear ends. The hot set up in a differential today is the True Trac. Actually, a 12 bolt Moser 33 spline True Trac is stronger then a 9" True Trac partly because it is bigger then the 31 spline offered in the Ford, and also because Moser has built up the original 12 bolt with their new castings. The other weakness in a 12 bolt is that the pinion tries to push the center chunk out of the back of the rear. A Performance cover takes care of this buy adding support to the center chunk main caps, which I have proven with 900+ HP in my street racer launching 100s of times on slicks with 1.30 short times. Now if True Track would make a 35 spline for the Ford like they do for the Dana / Moser 60s, that might turn things a bit.

So for GM guys I sell mostly 12 bolts with True trac's and with "Torino" (Ford Big Ends) and a performance support cover. If someone has a LOT of power, they are forced into a 35 spline Detroit Locker. Which if you ever had a Locker on the street, it is like driving a spool. UGH!

me. i have a spare 9" third that will go with the car on long trips, along with the tools needed for a change, as soon as the car runs, im driving down to arizona, from WA, hittin vegas on the way down :captain:

IMO its worse. i used to have a detroit in my dodge, (ramcharger) and it was downright scary. in the rain, wondering when it was going to ratchet in and out of full lock. :willy: sold it, got an open carrier and welded it.

One thing not mentioned here yet is that the pinion or yoke location is "lower" on a 9" than that of a 12bolt. This helps when building a "low" ride height car because you wont have to modify the trans tunnel as much on a 9" than you would on say a 12 bolt. It "hangs" low instead of being located in the center of the ring gear as on a 12 bolt.
I prefer the old skool 12 bolt with 35 spline axles, big ford ends and a girdle cover. But have used both.

it makes no difference at all what you choose, the 12 bolt is marginally lighter and has the advantage of the slightly higher pinion and accepting gm brakes.. z06 and "ls1" brakes.. but a fab 9 housing weighs the same, costs the same and 9 inch carriers can be bought to accept both 12 bolt, ford 8.8, 9 and 9,5 inch difs and gears.. and can be spec.'ed to accept both ford and GM brakes, so its a matter of preference...

Lets get rid of some of the mis-conceptions.

1. The newer 12 bolt housings are from the KTRE molds. The center section is made of ductile iron and they use 3.00" dia 4130 tubes. The main cap webbing has been reinforced, they use 1/2" fastners and the main caps are larger to combat cap distortion. The main caps themsleves are constructed of nodular 65-45-12 iron material.

2. The housing ends are not Ford, (although you can special order it with various other housing ends.) The housing ends are GM midsize, offered to fit 58503, 504 or 505 in a sealed bearing cartridge or a 58506 tapered roller bearing. The housings also use either 3.062 or 3.250" bore components.

3. A 35 spline axle in a 12 bolt is a no-no... unless you use a Mark Williams spool with a specific 'high pressure angle'. Not to mention that when you use an axle larger than a 30 or a 33 spline, the carrier journels become so thin that even normal street driving will snap the bearing journels clean off the carrier housing.

4. The difference in pinion height is 0.75", which equates to about 3.5% in efficiency. This higher pinion location in the 12-bolt results in lower gear lubricant temperature, improved fuel economy, and best of all, more power delivered to the ground... and its 30 pounds lighter.

5. A "third member" design differential housing is stronger in many aspects. The most obvious is that it allows the tubes to flex without effecting the carrier bearing pre-load, which in effect opens up the pinion to ring gear mesh. You can even use a 12 bolt third member... in a 9" housing to get the best of both worlds.

6. What the hell is a center chunk ?? Is that like a hogs heads or a pigs snout ??

7. Ratio availability goes to Ford, hands down. As does the simplicity of changing the center section with a different differential device and/or gear ratio. Although, it takes the same amount of time to swap gears in a 9" or a 12 bolt... just having a pre assembled third member makes it a litter eaiser and a-lot less messy.

8. The axle hop is related to a combination of the IC angle, from the pinion angle difference, and the height of the axle tube above the spring. A taller spring perch yields a longer torque arm on the spring itself.

All in all... its a wash. For a heavy car that can actually hook up a-lot of power... a 9" has its advantages. In a moderate weight car that is used on street and track/road course... either. In a lighter chassis with a firmer suspension... a 12 bolt. You can however spend more on a 9" than a 12 bolt in a heartbeat.

As always, VERY good tech, Tom. :thumbsup:

Thank you Chicane for professional input!! Wau!!:hail:

I stand corrected... my Dana 60 has the 35 with a spool and my 12 bolt, 33 with a posi. Both have the Big Ford End upgrade.

No they are not FORD, meaning a ford product. They are however referred to as ford housing ends.

commonly reffered to as the center chunk, center section, pumpkin, etc. :unibrow: but you allready knew that. :lol:

You can also get very good information from Mark Williams. I bought their 12 bolt modular setup for my car and am very happy with it. They walked me through the differences on all the different rears that would work for my car, both strengths and weaknesses.

For us budget guys... I just picked up a 9" in the local wrecking yard for nothing, they are full of them. Have you seen the price of a used 12 bolt lately, the option to go used in really no option-Chris:_paranoid

Not to split hairs... but, unless the housing end is a specific "Ford" bolt pattern, its not a Ford housing end. And they are not just refered to as a "Ford big bearing end".

There are a plethora of Ford, GM, Olds/Pontiac, Mopar and other non-make, symetrical housing ends. It is empathetically too generic to just say "Ford big bearing ends"... as there are six different big Ford ends. And if its not a Ford pattern... it is merely a housing end... which you then need to be even more specific on which one it is.

It is much eaiser to be understood when you dont speak in generalities. ;)

why so technical?
 

When you call Moser up and order a new 12 bolt does it make sense to get chevy style housing ends and run c-clips? Or just make it easy and order ford style housing ends and get the pressed bearing so you do not need to worry about c-clips. Why do have to make things so technical. I have been watching you here for months. It is obvious you have a wealth of technical information stored in your brain and you enjoy letting people know just how much technical info you have stored upstairs. Thank you, I do not know how myself and others would get by without the wealth of tech you so gladly fill these pages with. I always have my dictionary standing by too, so I can understand some of the technical words you like to throw around. Plethora, who even uses that word? Couldn't you have used a word like plenty, a lot, many. You know, something most people are used to seeing and using. P.S. I think you like splitting hairs.:)

LOL! That is something we have here in the south. Come on over to the racin track and well teach yall about center chunks! Luckily the guys at Moser are rednecks also, so they understand.

BTW, Chicane is correct. there are multiple Ford ends, and many are consdered "Big Ends", which like center cheunk, has become a familar slang.

As I said, when we order either a 12 bolt or a 9 inch, if the owner does not already have brakes, we specify Torino stlye ends, which use big Ford bolt patterns.

If I called up Moser and ordered a new 12 bolt with big bearing Ford ends... it just would not make any sense. Because they are not assembeled with big bearing Ford ends. They are assembeled with the Cheverolet, 'mid-size' pattern, housing ends. And you know what ?? They just happen to be a press-on style axle bearing end cup... similar to that of the Ford. But still somewhat different.

Why so technical you ask...?? Because I speak 'technical' and because at times, it is necessary to educate those who just dont get it. Case in point... "Chevy style housing ends" are not even part of this subject. In fact, they are not even a "style." We are not talking c-clip anything, in this thread. Now however, "Cheverolet mid-size housing ends"... that are Cheverolet pattern, are discussed. There is a huge difference.

I do not have a problem with those who disagree, offer other ideas or can debate a view point or theory, in fact, I implore it. But, if one were going to disagree or offer something else...etc, please, I simply ask that one will disagree intelligently.

Why do you make things out to be so generic ?? Knowledge and understanding of a specific subject isn't generic by any means. You ask a specific question and you will get an educated, and fairly specifc answer. If you generalize... well that is what you get in return and it may not answer your question at all. Like I said earlier, it is much eaiser to be understood when one does not speak in generalities.

If I were merely like the rest... (and those who know me will agree, that my personality screams something totally different)... life would be pretty damn boring. I have choosen to broaden my horizons, to educate myself per-se, so that I may convey the knowledge required for conversational needs... (without a 45 minute dissertation) and use them big ole' .50 cent words... 'cuz ninety-nine percent of my day is spent on a non-generic, higher level. Sorry... I guess.

I have however, made you look up three or four words now. So I guess you are learning something. ;)

I knew you would get a giggle out of that Frank. There are times that we speak the same dirt... :lol:

crossram, why even start the thread if you are so informed already?:thumbsup:

I highly value Chicanes technical knowledge an try to read and learn as much as i can. I had no idea how much differences could be between rear end an want to have mine right at once. Keep up the good word Chicane!

I guess I am mistaken about the new Moser 12 bolt I have sitting in my garage which has the big bearing ford housing end, and disc brakes for a ford housing end. Thanks for clearing that up. I will call Moser Monday and find out just what they sold me since they told me what housing end it had and what brake kit to get for it. If you really think I needed to look up your words, well I guess I let you keep thinking that, I feel for someone like yourself it is good for your ego.

You forgot to end that statement with Hero. :lol:

I have never once stated, that Moser and company were the sharpest tools in the shed. You got it that way, because you ordered it that way. I would hate to tell the 10,000+ late model F-body guys that are using the new 12 bolt that have to order the Ford brake package for the differential housing to work correctly.

You are really taking this too personally.

:lol:

...absolutely priceless.

9 bolts are plentiful
C clips are not allowed at the track
9 bolts are cheaper
9 bolt snouts are a bit stronger in the snout area (Moser 12 bolts have a beefed up snout area btw)

Its all in fun, loosen up.
 

You changed your tune pretty quick from they do not come that way, to you ordered that way. Yes, it was orderd that way. That is how I now they come that way. No, I am not taking it personal, I have actually been getting a pretty good laugh at how upset your were getting at something so trivial in life as this. You seemed to be wound up pretty tight and need to loosen up. It is called sarcasm. My original thread was intended to be sarcastic. There is not a person out there that would think of putting a ford powerplant in their GM car, so why put a 9" in it. That is all it was about. Most people do not need the added features a 9" has to offer for their inteded use of the beautiful pro-touring cars. Most cars a built for the appearence, creature comforts and a better all around ride. Plenty of people sacrifice some performance for that correct look they are trying to achieve.:cheers:

Pro touring
 

Yes 9" rears are plentiful. C-clips at the track, depends on the class, at least in the area where I reside, 9" rears are cheaper if you are comparing it to a camaro/nova 12 bolt. If you are going to buy new, not much of a difference in price. Yes 9" rears are stronger as you said. If I was building a 1/4 mile race car as with my 67 nova(which has a 9" w/strange spool, nodular center section, aluminum pinion support, 35 spline axles and 5/8" studs), a 9" would be the obvious choice. Since this is pro-touring web site the thread was not aimed at drag cars.

What about Ron DeRadd's twin turbo 302 Ford into a 68 Camaro then eh?
http://users.adelphia.net/~rderaad/index.htm

Go on, be a hater.

Tyler

This thread is hilareous - if it didn't look like an add for a couple of guys I would have thought I was on a kinder, gentler cc.com - but I'll pipe in anyways.

Another obvious reason that some of the more seriously built pt cars run ford 9" rears is that you can't run a 12 bolt with many of the aftermarket rear suspension offerings.

And comments about rear end strength being somehow less of an issue with pt cars vs straight line cars is definately naive. A lot of the members on this site push their cars hard in addition to putting a lot of miles - often spirited miles - on their cars. Generalities about how people will use their cars are just that - generalities.

You're choice for a rear end was obviously a personal choice and you seem pleased enough with your decision so congratulations on that.

The only one around here that has changed their tune, not to mention their song and dance, is some FNG known as 1969Crossram.

The "standard" housing end for the new 12 bolt is the GM mid-size bearing cup. Afterall, the 12 bolt and the mid-size GM bearing cups and their respective bolt pattern... are standard General Motors components. The new 12 bolt differential housing only comes with big bearing Ford ends if you order it that way. So, I am glad to see that you pony'ed up to that one finally.

Although possibly beyond your comprehension, I am not at all worked up over this in the least. Lemmings will be lemmings... but to see you hide your lament and chidingly misdirection, is the icing on the cake.

You do however, have a lot to learn about sarcasm (see above statement). You also have a lot to learn about the people on this board. With 14 posts... we'll leave this as your one and only reprieve.

And lastly... just as another venerable F-body master, Teetoe Jones, has pointed out... there are quite a few early and late model F-bodies (and other types) that are running cross bread.

Nice back peddling though...

http://img198.exs.cx/img198/9453/amywaffle5hq.gif

And your point is???
 

What is that, 1 in how many hundreds. Find a some more and you will have a point. Do you have a ford motor in your GM car? Would you put one in it? If you think a 12 bolt would not hold up to the rigors for the few who push their p/t cars to limit, you are wrong. Also, the two camaros you thought I was advertising for was just to show you how much abuse and power a well set-up 12 bolt can handle. A 1.3 short time (w/a 406)isn't too shabby. I think you will have to agree with that. When is the last time you saw a p/t car launch as hard as that car does with such a low 60' time? Rears see much of their abuse from a dead stop launching a 3000+ lb. car with a trans brake than a p/t car on a road course, or cruising cross country. Many aftermarket set ups will not accomadate a 12 bolt? You say many, I can think of Lateral Dynamics. What is the many you are referring to? DSE's stuff works fine with a 12 bolt. I have their quadra link for my 69, and their spring kit in my garage for my friends 69. Most guys build their p/t car do drive and enjoy. Their are the few willing to push their car to the limit and risk damaging it. Most would not want to risk all the time, money and sweat they have in their cars. Would you be willing to risk your $50,000 to $100,000 investment? I know I work too hard for my money to take a chance and push my car to the extreme and possibly smack a wall with it.

shwoooo I've been givin a reprieve form chicane
 

I did not specify it when it was orderded. They recomended for the application. If you read the post correctly you would see I never said I specified it that way. I merely said it was ordered that way. Theres no coming clean, I have one like that, big deal. I needed to tell you that why? I only told you because you were so persistant in the fact that you cannot get it that way. As far as the criticism of Moser. They appear to be doing something right. They have been in the racing world for a long time. If you are not upset, it sure doesn't come through that way in your post. SO let me get this straight, I need to tell you I have something in order for you not to say that it can't be bought that way. So there a couple cross breads (is that politically correct to use those words?) out of hundreds and hundreds. Hardly makes a point. You wear your buttons on your forhead for the pushin. You a pretty easy to get all fired up.:willy: :willy::bow: :bow: I am bowing down to you. Thank for the reprieve. Do not know what I would have done without your mercy.

above
 

Read above quote titled your point is, in response to your thread thanks.:)

doesn't appear any more tech info is coming out of this one, so I'll close it.

Jody