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Thread: What gearbox for my duratec mgb

  1. #1
    Spanner Monkey

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    What gearbox for my duratec mgb

    Hi everyone, I had been running my MGB GT with a 2.0 duratec for some time and thoroughly enjoyed it (very quick). But ive just built a R500 "spec" engine and looking at around 250-260bhp @ 8000RPM. My current gearbox is a type 9 V6 with BGH geartech layshaft bearing mod. Ive had no roblems with it but concerned that the greater power will be too much for it (or even the higher RPM). I'm considering modifying the gearbox to lubricate better or...... use an MX5 gearbox. But there is a 5 speed and a 6 speed. Ratios are as follows, with type 9 , 5 speed mx5, and 6 speed mx5.

    1st
    3.36
    3.136
    3.709
    2nd
    1.81
    1.888
    2.190
    3rd
    1.26
    1.330
    1.536
    4th
    1.000
    1.000
    1.177
    5th
    0.82
    0.814
    1.000
    6th
    -
    -
    0.832



    My final drive ratio is 3.9:1 and using 185/65R15 tyres. Is the first gear in the 6 speed too high a ratio? I don't want to have to change gear constantly. Also how much heavier is the 6 speed over the 5 speed as id like a lightweight car.

    Any advice will be gratefully received.

  2. #2
    Racer Decade Plus User

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    Re: What gearbox for my duratec mgb

    Based on ratio's i'd choose the MX 5 speeder all day long. You've got power and torque to use the ratios and Its apparently a stronger box overall and probably a few grams lighter. I've just changed my T9 first gear to a 2.98 ratio with a 3.54 axle ratio as the std 3.65 was ridiculously low so 3.709 mated to a 3.9 axle is rock crawler ratios! They are chunky boxes so a bit of tin bashing may be required.
    Mind you, I question your sanity shoving that much power into a BGT LOL!

  3. #3
    Spanner Monkey

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    Re: What gearbox for my duratec mgb

    Thanks for the reply, ill stick with the 5 speed then. If one comes up on ebay for a decent price ill go for it. Until then ill stick with the type 9 as funds are low. Ive had to replace over 20 panels on the MGB so far.

    As for my sanity, well I love fast cars and I love classic cars so combining the two made sense, and its great looking at the faces of BMW drivers as I pass them

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