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Thread: m21 gearbox

  1. #1
    casual poster hx tonner's Avatar
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    Talking m21 gearbox

    will a m21 handel 300 hp atws. if not what would be a better alternative that isn't to expensive. let me now wat you's think any help would be great.
    cheers

  2. #2
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    is it in your hx 1 ton and what ratio diff ?

    they can handle a fair bit , depends on its condition , they weight of the car the load placed on the box

    down shifting and shock loading do hurt these boxes so do roll backs and constant abuse .
    Last edited by ffsuc; 14-12-2009 at 06:48 PM. Reason: rooted

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    I busted one behind a 355 stroker with 250bhp and I was only running it in,Didnt rev over 4000rpm and drove it like a nanna...

    Ive also busted a few driving them hard in mild 308s

    They dont like abuse or torque...

    Dont waste your time mate,if ya want a 4 speed cog box go a top loader or muncie...
    Too many cooks spoil the broth...

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    casual poster hx tonner's Avatar
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    dont know as to the ratio the diff is sorry. the box is not in the car its out of a 253 hq ute.
    i can get a saganaw but in needs tlc an bell housing would this be a better option??????????????????????
    cheers

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    a saginaw is a pretty good box aswell,a mate of mine had one in a 12sec ht monaro and it lasted for years..
    Too many cooks spoil the broth...

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    Do you ever leave? DR327VK's Avatar
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    My M20 is still holding up! lol
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    casual poster hx tonner's Avatar
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    My M20 is still holding up! lol
    is the m20 in the vk or the wb
    . cheers mate

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    Do you ever leave? tonnergirl's Avatar
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    I was going to do that combo but didn't risk it and found a T350, glad I did now too
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  9. #9
    casual poster hx tonner's Avatar
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    tonnergirl
    I was going to do that combo but didn't risk it and found a T350, glad I did now too
    aw ok.
    i want to keep it manual

  10. #10
    Sure why not? 76lxhatch's Avatar
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    If your 300hp is real then it won't last long without a lot of mechanical sympathy in a heavier vehicle.

  11. #11
    casual poster hx tonner's Avatar
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    76lxhatch
    If your 300hp is real then it won't last long without a lot of mechanical sympathy in a heavier vehicle.
    300 is what im aiming for. me an my dad are starting a biuld
    if it ain't broke don't fix it. if it is broke modify it

  12. #12
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by hx tonner View Post
    will a m21 handel 300 hp atws. if not what would be a better alternative that isn't to expensive. let me now wat you's think any help would be great.
    cheers
    yes ..it will
    provided its in good nick to start with
    has decent oil (do NOT put a mix of ATF and hypoid in)
    and you dont go drag racing with it (and no burn out comps ok )

    I have one in my race car ..and its lasted 3 seasons now of competition . why..??
    Apart from the odd hillclimb they are all rolling starts and I spent a lot of
    time with clearances getting them right and it has 140w comp hypoid oil in it
    AND
    the shifter is set up properly

    btw
    300rwhp means you will be aiming for a heavy breathing 380-400fwhp good luck
    Last edited by Smitty2; 14-12-2009 at 11:19 PM.
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    casual poster hx tonner's Avatar
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    cheers mate love my burnouts . might have to keep it low key
    does anyone know if a t5 out of a vs 5 litre will bolt up to a 308 an wat mods are need to do this. cheers
    if it ain't broke don't fix it. if it is broke modify it

  14. #14
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    Quote Originally Posted by Smitty2 View Post
    yes ..it will
    provided its in good nick to start with
    has decent oil (do NOT put a mix of ATF and hypoid in)
    and you dont go drag racing with it (and no burn out comps ok )

    I have one in my race car ..and its lasted 3 seasons now of competition . why..??
    Apart from the odd hillclimb they are all rolling starts and I spent a lot of
    time with clearances getting them right and it has 140w comp hypoid oil in it
    AND
    the shifter is set up properly

    btw
    300rwhp means you will be aiming for a heavy breathing 380-400fwhp good luck
    mine was fully rebuilt smitty,

    I wouldnt risk it..If ya gonna spend the money on the engine then spend some on the rest of your driveline..You'll thank me later...

    do it once do it right.......
    Too many cooks spoil the broth...

  15. #15
    Do you ever leave? DR327VK's Avatar
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    Quote Originally Posted by hx tonner View Post
    is the m20 in the vk or the wb
    . cheers mate
    M20 is in my VK burnout car and has 300rwhp

    My WB has TH350 which is so far unbreakable!
    ....Just Street Performance...
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