Thread: Need help identifying my new muncie tranny

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I just bought this muncie 4 speed today, I'm not sure about what gear ratios it has. I believe it is a m-20 from what i've been seeing. The main case numbers are 3885010. Rear tail is 3846429. Patent number is 3088336. The front shaft is 10 spline with 2 rings in the spline. Any good websites for this kinda stuff? Thanks for any info.

With two rings and a 10-spline input shaft, it's a 1966-1970 M20.

Ratios are: 2.52, 1.88, 1.46, 1.00

http://www.5speeds.com/muncie2.htm

Thanks Henry, that website makes it pretty easy to identify. I'm glad it's not the close ratio, I was wanting to go with 3.73 gears. From what I've been reading you would need 4.56's to go well with the m21/m22's first gear.

http://www.camaros.org/trans.shtml#MuncieRatios
http://www.chevellestuff.com/generic/muncie.htm
http://www.camaros.org/trans.shtml

Your M20 with a 3.73 is equivalent to a 4.25 in a close ration M21 or M22. If you're using a BB Chevy, you've got enough HP and torque that you don't need the narrower spread.

Thats what I figured, I'll have enough torque and a wide powerband to work well with the wide ratio. A hot 327 might need the m21 or m22, or maybe an LS6 454. Have you seen the cam specs of those? 264 duration @.050?