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Old 03-09-2004, 02:21 PM
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Transmission swap - Auto to Manual

I am thinking about swapping out my TH400 in my 1969 GTO with a muncie 4 speed. I am wondering how much I am looking at changing, such as driveshaft etc. I have a Pontiac 400 engine and as I said, the TH400 transmission. Also, what are the pros and cons of a m20, m21, or m22. Which would be the better choice?

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Old 03-09-2004, 03:26 PM
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As far as I know the main difference between the M-20 and M-21 is that the 20 is a wide ratio and the 21 is a close ratio. And the M-22 "Rockcrusher" has straight cut gears which makes it stronger and noisier.
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Driveshaft and yoke, trans crossmember and mount. Then you will have to wire up an electric switch for the kickdown, and of course a shifter and maybe a reverse and neutral safety switch. It's a real ****** gettin run over by your own car. Of the Muncie 4-spds the one to use on the average muscle type street car is the 2.54 low wide ratio. The M-22 is way overrated, noisy, and has a 2.20 low gear. This is ok if you have a 4.10 or better.
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