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Thread: MX5 or RX8 Gearbox?

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    MX5 or RX8 Gearbox?

    Evening all,

    As title really, which box is gonna be bext for me to use on a turboed zetec? Both plentiful and dead cheap

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    World Champion Decade Plus User alladdin's Avatar

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    Re: MX5 or RX8 Gearbox?

    ford mt75 easier ? you dont need the c ratio of the rx8 with turbo ?

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    Re: MX5 or RX8 Gearbox?

    What's the C ratio?

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    Re: MX5 or RX8 Gearbox?

    Quote Originally Posted by alladdin View Post
    ford mt75 easier ? you dont need the c ratio of the rx8 with turbo ?
    And yes, the MT75 would be easier but there's far less of them around than the others and theyre more money!

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    Re: MX5 or RX8 Gearbox?

    Quote Originally Posted by Daveysaff View Post
    What's the C ratio?
    Close Ratio.
    One other thing is that 1st is virtually unusable with the Mazda boxes (unless you tow a caravan!)

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    Re: MX5 or RX8 Gearbox?

    Is that true of the 5 speed RX8 box too? I know first gear on the 6 speed is a waste of time

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    Re: MX5 or RX8 Gearbox?

    Quote Originally Posted by Daveysaff View Post
    Is that true of the 5 speed RX8 box too? I know first gear on the 6 speed is a waste of time
    I believe it is lower than a std Type E / T9 box 3.65:1 which I consider nearly un-usable LOL! Maybe using 15 or 16" wheels makes a difference (obvs!)

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    Re: MX5 or RX8 Gearbox?

    It’ll be on at least 16” to clear the brakes so fingers crossed it’ll work well for me!

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    World Champion Decade Plus User alladdin's Avatar

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    Re: MX5 or RX8 Gearbox?

    Quote Originally Posted by katana View Post
    Close Ratio.
    One other thing is that 1st is virtually unusable with the Mazda boxes (unless you tow a caravan!)
    i disagree - if you look at it as a close ratio 5 speed box (and thats why its popular after all ) then the 2nd gear (new 1st !) is actually higher than the quaif "rally" 1st gear and as such if you using in traffic / town or wales ( i live on a near vertical hill ) then whilst 1st is lower than you want its certainly an added free bonus

    Quote Originally Posted by Daveysaff View Post
    It’ll be on at least 16” to clear the brakes so fingers crossed it’ll work well for me!
    turbo and 16" wheels - buy a sierra

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    MX5 or RX8 Gearbox?

    Have you seen how much a rot free Sierra costs!!
    Besides, I’ve had one of them already 🤪


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    Re: MX5 or RX8 Gearbox?

    Quote Originally Posted by Daveysaff View Post
    It’ll be on at least 16” to clear the brakes so fingers crossed it’ll work well for me!
    You don't say what diff ratio you are thinking of using with your 16 inch wheels Davey. If you are using a tall ratio in the diff then the low first gear of the 6 speed Mazda box might just come in handy for hill starts and slow traffic. You then still have 5 close ratios to play a tune on.

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    MX5 or RX8 Gearbox?

    Quote Originally Posted by Forest_rallying View Post
    You don't say what diff ratio you are thinking of using with your 16 inch wheels Davey. If you are using a tall ratio in the diff then the low first gear of the 6 speed Mazda box might just come in handy for hill starts and slow traffic. You then still have 5 close ratios to play a tune on.
    I’ll be the first to admit I know naff all about diff/gear ratios to its deffo something I’ve got to learn.
    I’ve picked up a JDM mx5 back end to get cracking with, I believer that’s a 4.1:1


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    MX5 or RX8 Gearbox?

    I’ve now collected an NA mx5 gearbox for the princely sum of £20
    Now to start researching clutches and spigot bearings


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    Re: MX5 or RX8 Gearbox?

    I'm currently running an MX5 NB 5speed for track days. Nice gearbox when it comes to gear switching but there is a large gap between 2nd en 3rd gear. Making it very difficult to find the right gear for cornering. And it is just about the speed you are normally into when cornering.

    The MX5 6speed and RX8 have much better gear spread. These boxes are about the same from second to 6th as a close ratio 5 speed for a fraction of the price.

    I would go for RX8 and spacer (available on internet). Don't think there are spacers kids for the MX5 NB box. MX5 NC will fit straight onto a Duratec engine, unfortunately, not on the Zetec.

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    Racer Decade Plus User wildo105e's Avatar

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    Re: MX5 or RX8 Gearbox?

    Quote Originally Posted by onyd View Post
    MX5 NC will fit straight onto a Duratec engine, unfortunately, not on the Zetec.
    Retroford do a complete kit to fit it now to the Zetec. If that helps

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    Re: MX5 or RX8 Gearbox?

    RX8 gearbox is approx the same box, cheaper and adaptors available

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