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why 12 bolt for A4, n?ot 9"

This is a discussion on why 12 bolt for A4, n?ot 9" within the Automatic Transmission forums, part of the Drivetrain category; Title bought says it all. Why cant I run a 9" with a A4? Im sure I can, but why ...

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    T/A Everyday oreowizard's Avatar
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    Question why 12 bolt for A4, n?ot 9"

    Title bought says it all. Why cant I run a 9" with a A4? Im sure I can, but why does most everyone promote the 12 bolts? Is it any 12 bolt that I can find in a junk yard? Not trying to be cheap but would like to save a lil $. Thanks for the input.

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    2001 z28 lingenfelter 383

    what are your mods/future mods? do u race your car at the strip? everyone says 12 bolt for auto and 9 inch for 6 speed because u really dont NEED more than a 12 bolt in most cases with an auto...if your not planning on modding much and no plans for the strip just buy another 10 bolt dirt cheap and throw it in if yoru tryin to save money

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    2 SS's are better than 1 Jays00ss's Avatar
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    In my opinion I would buy a 9" no matter what tranny I had. They are Stronger, easier to work on, Cheaper, and have a lot more options on what you want in the build up.

    I have a 9" and absolutely love it in My Camaro. I have had many muscle cars with both 12 bolts and 9" fords and find the 9"'s just an all around better rearend no mater what Car I have owned.

    Don't get me wrong My 12 bolts in my older stuff was just fine without the torque arm mount set up, But I have read and reasearched the the 9" is the way to go with these new gen f-bodys.
    2000 SS Camaro Heads, Large cam, Fast 90, 9"w/430's and locker, yada yada yada... you get the picture

    1971 SS ElCamino 402 Big Block 550HP

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    T/A Everyday oreowizard's Avatar
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    Only a few bolt ons in/planned. Lid, LS6 intake, Full Exhaust. 150shot coming soon. May run it on the track a few times a year. Just a DD

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    Senior Member slims00ls1z28's Avatar
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    I'm with Jay on this. I too have a 9". I heard all to much about stuff like case distortion etc with the 12 bolt. Plus I have bigger plans for the car and didn't want to have to worry about it when I start yanking the wheels. Why play second fiddle? Go all out once.

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    T/A Everyday oreowizard's Avatar
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    If I'm not wanting to strip race it a lot, would a 10 bolt be okay?

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    with 150 shot of nitrous and other mods, I would trust the 10 bolt. Im afraid to launch mine hard with only a cat back and good tires.

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    2 SS's are better than 1 Jays00ss's Avatar
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    Quote Originally Posted by oreowizard View Post
    If I'm not wanting to strip race it a lot, would a 10 bolt be okay?
    I have seen guys grenade thier 10 bolt that are completely stock. Its up to you, Pay now or pay later and I hope you know a buddy with a truck and trailer.

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    It doesn't make sense to run a ford product in a GM car, their larger and some, not all, things don't match up...at all. Moser works fine for me $2200 to my door

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    Senior Member splitfinger09's Avatar
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    Quote Originally Posted by fabrizi View Post
    It doesn't make sense to run a ford product in a GM car, their larger and some, not all, things don't match up...at all. Moser works fine for me $2200 to my door
    Ok so theres a difference between a ford 9 and a moser 9?

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    2 SS's are better than 1 Jays00ss's Avatar
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    Quote Originally Posted by splitfinger09 View Post
    Ok so theres a difference between a ford 9 and a moser 9?
    It is an after market design on the old ford 9" that has been around since the late 50's into the early 80's. Racers have been using them ever since they were introduced. They are one of the best rear end designs you will find.

    I figure if top fuel, funny cars, pro stock and Nascar all run versions of them something must be working just fine.

    As far as being "ALL chevy" the Moser 12 bolt is after market just like the 9" and neither chevy nor ford makes them.

    I have had both the 12 bolt and the 9" in my muscle cars over the years and the 9" is just a better design. Don't get me wrong I am a chevy/gm fanatic and have been all my life but come on, I and a lot of people can say that the 9" is an awesome design and stronger, more reliable than the 12 bolt.

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    Member nomorefords's Avatar
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    Quote Originally Posted by Jays00ss View Post
    In my opinion I would buy a 9" no matter what tranny I had. They are Stronger, easier to work on, Cheaper, and have a lot more options on what you want in the build up.

    I have a 9" and absolutely love it in My Camaro. I have had many muscle cars with both 12 bolts and 9" fords and find the 9"'s just an all around better rearend no mater what Car I have owned.

    Don't get me wrong My 12 bolts in my older stuff was just fine without the torque arm mount set up, But I have read and reasearched the the 9" is the way to go with these new gen f-bodys.
    hey i was just doing some research about 12 bolts and 9 in rears and from what it sounds like the 9 inch isn't the way to go with our f-bodies because of the use of the torque arm. The article is in one of the newer Chevy specific mag's, i can't remember which one exactly but it should still be out on newstands. Is this article feeding me the wrong info, and by no means am i saying you're incorrect just trying to educate myself and find out if it's a legit write up, or should i purge it from my brain!
    2002 Electron Blue Z06, Performance Bir Break Kit, Vararam Intake, Borla Quad Tip Stingers

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    Senior Member Zboner's Avatar
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    Quote Originally Posted by nomorefords View Post
    hey i was just doing some research about 12 bolts and 9 in rears and from what it sounds like the 9 inch isn't the way to go with our f-bodies because of the use of the torque arm. The article is in one of the newer Chevy specific mag's, i can't remember which one exactly but it should still be out on newstands. Is this article feeding me the wrong info, and by no means am i saying you're incorrect just trying to educate myself and find out if it's a legit write up, or should i purge it from my brain!

    totally wrong information from the artical, the best part of the 9" if the TQ arm mount.

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    Member nomorefords's Avatar
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    Quote Originally Posted by Zboner View Post
    totally wrong information from the artical, the best part of the 9" if the TQ arm mount.
    see that's what i like to hear back, simple concise response. a lot of guys get on here after reading an article and throw it in peoples face like they know whats up. i'm all about education, and i'd rather hear how it taste from the horse's mouth not it's ass! I've been looking into the 9 or 12 and couldn't decide with the conflicting info. So you think the 9 would be the way? I'm putting a build 4l60 with a shift kit in soon with 3500 stall and 100 shot so i don't know how long the 10 bolt had till it's demise!

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    Senior Member Zboner's Avatar
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    yea personally i went with the 9" and full spool, (dont drive mine that often) and no complaints so far. and i went through 6 4L60E's lol with my Z28

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    2 SS's are better than 1 Jays00ss's Avatar
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    Quote Originally Posted by nomorefords View Post
    hey i was just doing some research about 12 bolts and 9 in rears and from what it sounds like the 9 inch isn't the way to go with our f-bodies because of the use of the torque arm. The article is in one of the newer Chevy specific mag's, i can't remember which one exactly but it should still be out on newstands. Is this article feeding me the wrong info, and by no means am i saying you're incorrect just trying to educate myself and find out if it's a legit write up, or should i purge it from my brain!
    I will Quote Bob At EPP

    "Put a 12 bolt into a early Chevelle, Nova, Camaro, etc and you can beat the crap out of it, and not hurt anything. Put one into one of our cars with a torque arm, make a couple 4000 to 5000 dragstrip launches, and I can just about guarantee you'll pick up gear noise. If it is a drag only car, you'll never know or care about the gear noise. Drive your car home from the track, and the noise will drive you nuts. I feel the torque arm stresses the 12 bolt housing, causing distortion. We have never seen this happen with the 9 inch housing.


    Exotic Performance Plus strongly recommends the Moser nine inch. This rear is even tougher than the Moser 12 bolt, and the horsepower of the late model F Body cars keeps escalating every year, which requires a very strong rear. With the recent introduction of the 6.2L GM aluminum block and the excellent flowing 6.2 litre heads, the horsepower of these cars is going to just keep climbing at a very fast pace.The nine inch will handle the power, plus we prefer the way the torque arm is bolted to the nine inch in the same way the oem rear-end is attached. (This is the only good thing about the stock 10 bolt...) The Moser 12 bolt uses four short bolts to attach the torque arm, and they have a habit of loosening up, even when loc-tite is used. Why the nine inch is stronger than the 12 bolt. The 9-inch has an internal rear-pinion support that also supports the gear end of the pinion to limit gear deflection under high torque loads. This seems to be the major reason why the 9 inch doesn't start whining after high rpm clutch dumps, when the 12 bolt will pick up noise.The 9-inch locates its pinion gear lower on the ring gear to improve tooth contact, than the 12 bolt does.The 9-inch has a 0.125-inch larger ring-gear diameter and internal pinion support than the 12 bolt does. This is not much of a difference, but it is worth noting. "

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    T/A Everyday oreowizard's Avatar
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    where is the best price on a Moser 9? Is it an exact bolt-in replacement, or does it require fabbing?

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    Are you guys running floaters? I thought those usually required the hats that stick through the hubs.

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    2 SS's are better than 1 Jays00ss's Avatar
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    Quote Originally Posted by oreowizard View Post
    where is the best price on a Moser 9? Is it an exact bolt-in replacement, or does it require fabbing?
    I bought mine for $2550 shipping included. It is a Moser case with drain plug and 35 spline axles with reluctor rings installed, Strange Pro Nodular third member with Motive Performance 4,30 gears and a Detroit locker. It is a bolt in replacement However there are a couple of things that you need to do.

    1) You need to buy a conversion u-joint because it comes with a much larger 1350 yoke.

    2) you need to buy 2 EA 3" exhaust clamps to mount your sway bar.

    3) the torque arm mount might need some material removed. (It depends on what torque arm you use) and Moser even states you can do this.

    4) you have to do a very little bit of sheetmetal modification around the area where the torque arm mounts (push up the metal a little bit for clearance you will not notice it from inside the car)

    5) the Moser 9" houseing does not have brackets for the brake lines. I used those real Fat zip ties and it looks fine.

    6) you will have to have the wheel bearings pressed onto the axle after you put your old brake backing plates on from your 10 bolt.


    Thats about it. 2 people can have it done in a weekend with plenty of refreshment breaks inbetween.

    The price I paid was for an extremely aggressive unit. If you went with a regular strange nodular case, 31 spline axles and a Detroit tru-trac. It will be around $2200. This might be the better route and it will be much more quieter than haveing a detroit locker.
    Last edited by Jays00ss; 12-13-2007 at 02:09 PM.

  20. #20
    Member nomorefords's Avatar
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    Quote Originally Posted by Jays00ss View Post
    I will Quote Bob At EPP

    "Put a 12 bolt into a early Chevelle, Nova, Camaro, etc and you can beat the crap out of it, and not hurt anything. Put one into one of our cars with a torque arm, make a couple 4000 to 5000 dragstrip launches, and I can just about guarantee you'll pick up gear noise. If it is a drag only car, you'll never know or care about the gear noise. Drive your car home from the track, and the noise will drive you nuts. I feel the torque arm stresses the 12 bolt housing, causing distortion. We have never seen this happen with the 9 inch housing.


    Exotic Performance Plus strongly recommends the Moser nine inch. This rear is even tougher than the Moser 12 bolt, and the horsepower of the late model F Body cars keeps escalating every year, which requires a very strong rear. With the recent introduction of the 6.2L GM aluminum block and the excellent flowing 6.2 litre heads, the horsepower of these cars is going to just keep climbing at a very fast pace.The nine inch will handle the power, plus we prefer the way the torque arm is bolted to the nine inch in the same way the oem rear-end is attached. (This is the only good thing about the stock 10 bolt...) The Moser 12 bolt uses four short bolts to attach the torque arm, and they have a habit of loosening up, even when loc-tite is used. Why the nine inch is stronger than the 12 bolt. The 9-inch has an internal rear-pinion support that also supports the gear end of the pinion to limit gear deflection under high torque loads. This seems to be the major reason why the 9 inch doesn't start whining after high rpm clutch dumps, when the 12 bolt will pick up noise.The 9-inch locates its pinion gear lower on the ring gear to improve tooth contact, than the 12 bolt does.The 9-inch has a 0.125-inch larger ring-gear diameter and internal pinion support than the 12 bolt does. This is not much of a difference, but it is worth noting. "
    thanks for the knowledge yo, and let me reiterate the point that i wasn't saying you were wrong, just trying to get things right on my side. but i appreciate the feedback, because it's literally going to save me a lot of money in the future, cause i absolutely hate gear noise, and i would be ready to kill somebody everytime i drove if i spent $2k or more and all i heard was whining!

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