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rear end

This is a discussion on rear end within the Drivetrain forums, part of the LSx Technical Help Section category; how much is a good 12 bolt and would it be worth buying over a 9 inch...

  1. #1
    Junior Member stormkarma's Avatar
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    rear end

    how much is a good 12 bolt and would it be worth buying over a 9 inch

  2. #2
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    '02 WS.6 / '07 Suburban

    I bought a Moser 12 bolt in December for our car. I added 33 spline axles, a True Trac, 4 channel ABS, welded relocation brackets and welded sway bar brackets for a total of $2,800.00. You can check it out in this thread: Bidding my rear adieu!

  3. #3
    Junior Member stormkarma's Avatar
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    Wink damnit jeffry

    your the man awsome build got me drewling on my laptop
    thanks for all the info

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    Veteran Hi-Po's Avatar
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    They both have pros and cons and will almost always cost the same.

    12 Bolt Pro's :

    1. Factory GM rearend. Some people enjoy having all GM parts on their ride.
    2.Easier to keep TCS and ABS and not have issues with the system.
    3. Slightly lighter, slightly

    12 Bolt Cons :
    1. Torque arm mounting location can add additional gear whine after a few passe's at the track.
    2. No removable center section - Your stuck with the gear ratio you choose.
    3. Slightly weaker then Ford 9". The amount weaker is heavily debated on, with the being that the ring gear is actually smaller in size

    9" Pro's :
    1. Torque arm location is removed from the center of the carrier and offset on 3 mounting posts. Usually resulting in less track induced gear whine and looked upon as being a stronger design
    2. Removable center section. Allows racer to swap gear sets in a matter of hours without having to set up gears and deal with pesky crush sleeves
    3. Seemingly more forgiving to 6 speed manual cars

    9" Cons :
    1. Slightly more horsepower loss.
    2. Slightly heavier
    3. Non GM part. ABS, TCS is an upgrade and has been known to give problem resulting in codes being thrown. Seems to be more dominant in 3 series carriers where the reluctor ring pick up in located inside the housing
    4. Being non GM turns away a small percentage of people. Realistically, if your installing a beefed up rearend, your problem heavily modded and any collector value was already shot.

    Thats the jist of the two rearends. The rule of thumb is manual cars pick the 9" to play and autos team up with the 12 bolt. Ive ran both 12 bolt and 9" in my manual, and must say the 12 bolt had a considerable amount more gear whine.
    370 CI - Twin 6766 Turbo - Jakes stage 5 4L80E - MWC 9" - Holley Dominator

    Build in progress...

  5. #5
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    I've been pondering the torque arm setup on my 12 bolt as I also upgraded to a UMI tunnel mount. Clearly, the metal-on-metal setup is going to transmit more noise into the cabin -- I fear that the poly bushings in the mount and arm will do little to reduce this.

    Since I need a little more clearance for my PST driveshaft anyway, I am going to install a rubber spacer between the tunnel brace and the body. Most likely, I will utilize the new rubber strap from an exhaust hanger set as it seems fairly dense. I will probably install it with longer bolts and see if I can squeeze a nylock nut in there as an extra safety measure, in addition to dousing it with thread locker.

    Under load, the torque arm will be pulling up on the tunnel mount so I shouldn't have any issues. This will hopefully give it just a bit of cushion and hopefully cut down on noise. I lived with a banging exhaust on our Corvette for a summer and that seriously sucked. Thoughts?

  6. #6
    Junior Member stormkarma's Avatar
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    to pajeff and hipo thanx to you guys as well as a few others. you guys are brilliant and shoot info str8 forward with more facts and less opinions thanx
    cant wait for my car to compare to yours
    i have never owned or operated an ls1 this is all new to me

  7. #7
    Senior Member MrMasterCraft's Avatar
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    2002 C5 - M6 - Blue
    2000 Z28 - A4 - Pewter

    Quote Originally Posted by stormkarma View Post
    to pajeff and hipo thanx to you guys as well as a few others. you guys are brilliant and shoot info str8 forward with more facts and less opinions thanx
    cant wait for my car to compare to yours
    i have never owned or operated an ls1 this is all new to me

  8. #8
    Member joedude02's Avatar
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    Quote Originally Posted by Hi-Po View Post
    They both have pros and cons and will almost always cost the same.

    12 Bolt Pro's :

    1. Factory GM rearend. Some people enjoy having all GM parts on their ride.
    2.Easier to keep TCS and ABS and not have issues with the system.
    3. Slightly lighter, slightly

    12 Bolt Cons :
    1. Torque arm mounting location can add additional gear whine after a few passe's at the track.
    2. No removable center section - Your stuck with the gear ratio you choose.
    3. Slightly weaker then Ford 9". The amount weaker is heavily debated on, with the being that the ring gear is actually smaller in size

    9" Pro's :
    1. Torque arm location is removed from the center of the carrier and offset on 3 mounting posts. Usually resulting in less track induced gear whine and looked upon as being a stronger design
    2. Removable center section. Allows racer to swap gear sets in a matter of hours without having to set up gears and deal with pesky crush sleeves
    3. Seemingly more forgiving to 6 speed manual cars

    9" Cons :
    1. Slightly more horsepower loss.
    2. Slightly heavier
    3. Non GM part. ABS, TCS is an upgrade and has been known to give problem resulting in codes being thrown. Seems to be more dominant in 3 series carriers where the reluctor ring pick up in located inside the housing
    4. Being non GM turns away a small percentage of people. Realistically, if your installing a beefed up rearend, your problem heavily modded and any collector value was already shot.

    Thats the jist of the two rearends. The rule of thumb is manual cars pick the 9" to play and autos team up with the 12 bolt. Ive ran both 12 bolt and 9" in my manual, and must say the 12 bolt had a considerable amount more gear whine.
    how is this true? you can change your ring and pinion accordingly to your set up. it doesn't make as easy as a simple bolt on, but a good project for a day.

  9. #9
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    Quote Originally Posted by stormkarma View Post
    to pajeff and hipo thanx to you guys as well as a few others. you guys are brilliant and shoot info str8 forward with more facts and less opinions thanx
    cant wait for my car to compare to yours
    i have never owned or operated an ls1 this is all new to me

    Glad to help. Hi-Po has been at the LS game a lot longer than I have and has actually taught me a lot. After we bought our car in August of 2008, I knew I was going to need some assistance and I found all the help I have needed right here.

  10. #10
    Veteran Hi-Po's Avatar
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    Quote Originally Posted by joedude02 View Post
    how is this true? you can change your ring and pinion accordingly to your set up. it doesn't make as easy as a simple bolt on, but a good project for a day.
    Maybe you missed the 3rd member part. Point being, you can have an extra gear set (3rd member) laying around to swap in for different avenues of racing. I'm not saying the 12 bolt can never swap a gear ratio Come on, you didn't really read that far into it did you?

    Most guys are not are not willing to setup their rear ends. The point being made was that if you wanna drag race on Wednesday, then Thursday have a streetable gear again, you don't have to set up the rear end every time.

  11. #11
    Member joedude02's Avatar
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    well, then that's what should've been stated.
    moving on from this.

  12. #12
    Veteran Hi-Po's Avatar
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    Quote Originally Posted by pajeff02 View Post
    Glad to help. Hi-Po has been at the LS game a lot longer than I have and has actually taught me a lot. After we bought our car in August of 2008, I knew I was going to need some assistance and I found all the help I have needed right here.
    I learned from all the guys on here and failing the first time around on installs
    Quote Originally Posted by joedude02 View Post
    well, then that's what should've been stated.
    moving on from this.
    I'll edit the post and make a note that the 12 bolt center section is not welded into place and is removable.

  13. #13
    Junior Member stormkarma's Avatar
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    hi-po make a mistake
    human afterall

  14. #14
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    2002 Z28 A4 NBM
    Sadly now demodded :(

    I knew what he meant. The again I've had a 68 Mustang GT with a 9" and several different Chevy's with 12 bolts.

  15. #15
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    I also understood exactly what he meant. You can swap out a center section on a 9" in a matter of a few hours. Changing the gears in a 12 bolt is far more involved and requires specialized tools.

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