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Rear Gear

This is a discussion on Rear Gear within the GTO forums, part of the Vehicle Specific category; i was starting to look into rear end gearing and possible improvements that can be made to it. i know ...

  1. #1
    Insurgent Hunter dethinboots's Avatar
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    Rear Gear

    i was starting to look into rear end gearing and possible improvements that can be made to it. i know that all 04-06 models run 3.46 gears, but what does that mean? lol sorry. and what true improvements (ie hp and 1/4 time) would say going to a 3.70, 3.91, or 4.11 do?
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    It's hard to say really. You won't see any difference in HP. Traction will be the issue with running 3.91s or higher. The difference between 3.70s and stock is not worth the $$$. I know when I added 4.10s to my camaro it accelerated faster but had I had more issues with traction too. I don't feel the need to mess with the gears in my GTO.

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    Insurgent Hunter dethinboots's Avatar
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    okay thank you for the clarification. i love the stock torque and traction produced by the normal gears and would hate to lose top end because of lower gears.

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    Smiles for 9.5 Years cammed goat's Avatar
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    Stock gears should suffice.

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    cutting and welding mark21742's Avatar
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    I made the jump up to 4.56 gears in mine when I did my Ford 9" strait axle swap...looks like I'll be taching around 3,000-3,200 at 60mph with 31-18.50 15" tires.

    Unless you are heavily modified (huge cam, high stall) from what I've been told you really won't benefit from a gear swap. (I'm running a high compression 408 with a 255/263 .624/.624 115 lsa cam, so I pretty much needed taller gears since my engine makes power from just under 4000 rpms up past 8,000 rpms)

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    Insurgent Hunter dethinboots's Avatar
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    thanks for the clarification all

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    Former Mopar Man 2002ssslp's Avatar
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    Quote Originally Posted by dethinboots View Post
    okay thank you for the clarification. i love the stock torque and traction produced by the normal gears and would hate to lose top end because of lower gears.
    You be thinking about changing the entire rear for a 12 bolt, 9", S60. It sounds like you are racing the car and the stock 10 bolt will never hold up. Also, your car will top out over 155 mph. you will not lose that much mph with 3.90 gears and how often are you running at that speed. JMHO

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    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
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    Quote Originally Posted by 2002ssslp View Post
    You be thinking about changing the entire rear for a 12 bolt, 9", S60. It sounds like you are racing the car and the stock 10 bolt will never hold up. Also, your car will top out over 155 mph. you will not lose that much mph with 3.90 gears and how often are you running at that speed. JMHO
    The GTO has a fully independant rear, changing to a sold axle 12-bolt would take a substantial amount of modification.

    Though it is a 10-bolt aside from whining, I have'nt seen too many of the same complaints with the GTO differential as the f-bodys' solid axle 10-bolt diff.

    Mostly it seems it's the stock mounts, and half shafts, that are the issue when building power in the GTO.

    Though I could be wrong.

    just my .02
    Last edited by Smittro; 01-12-2012 at 07:15 AM.

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    Senior Member TLS_Addict's Avatar
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    You wont lose any top end...............they shut off between 155-160. Ask me how I know.

    The reason the GTO feels good with the 3.46 is it better ratios in the first 4 gears. That .57 OD is fine with 3.9X gears. It will still run 150+ but you will have a much snappier feelings car and with close to 4k lbs it needs some help.

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    None Shall Pass Knight's Avatar
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    Quote Originally Posted by Smittro View Post
    The GTO has a fully independant rear, changing to a sold axle 12-bolt would take a substantial amount of modification.

    Though it is a 10-bolt aside from whining, I have'nt seen too many of the same complaints with the GTO differential as the f-bodys' solid axle 10-bolt diff.

    Mostly it seems it's the stock mounts, and half shafts, that are the issue when building power in the GTO.

    Though I could be wrong.

    just my .02
    I agree. I recall seeing an article Ed posted about a 9" IRS conversion for the GTO, iirc. I'll see if I can find it.

    Quote Originally Posted by TLS_Addict View Post
    You wont lose any top end...............they shut off between 155-160. Ask me how I know.

    The reason the GTO feels good with the 3.46 is it better ratios in the first 4 gears. That .57 OD is fine with 3.9X gears. It will still run 150+ but you will have a much snappier feelings car and with close to 4k lbs it needs some help.
    I looked, but didn't see if the OP stated if he was an A4 or M6. If he's a M6, I'd say go with the 4.11s. An A4, 3.73 or 3.90 would be perfect. Either will wake the car up down low, without sacrificing anything but above 150 mph. Not normally an issue........unless he's like me or you

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    None Shall Pass Knight's Avatar
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    Here's the link to the article Ed posted about the conversion - Strange 9-Inch Coversion Kit - Smashing Pumpkins

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    cutting and welding mark21742's Avatar
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    Off topic, but you would be shocked by how much weight I dropped when I went to a solid axle 9"

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    Insurgent Hunter dethinboots's Avatar
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    a4 btw

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    cutting and welding mark21742's Avatar
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    If you go big cam with a big stall, then since you are an auto I'd put a set of gears in just to help your tranny last longer. With a higher stall your converter clutch will stay unlocked more, and work harder to lock.....I went through 4 4l60's in mine.....converter clutch would go out, then take out the front pump

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    Senior Member TLS_Addict's Avatar
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    Quote Originally Posted by Knight View Post
    I looked, but didn't see if the OP stated if he was an A4 or M6. If he's a M6, I'd say go with the 4.11s. An A4, 3.73 or 3.90 would be perfect. Either will wake the car up down low, without sacrificing anything but above 150 mph. Not normally an issue........unless he's like me or you
    I am nothing like you.

    I am thinking of some gears for the Vette already. 1200 RPMS at 55 mph.......


    Quote Originally Posted by dethinboots View Post
    a4 btw
    3.46 to 3.73 you would notice something but I would go to 3.90s. Maybe run a little taller tire if possible if you want more take off and a larger foot print.

  16. #16
    cutting and welding mark21742's Avatar
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    I have plenty of room for a 33- 22.50 15 under my goat

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