# What's the difference between a M20 and M21 Muncie 4-speed?



## extinctmake (Feb 8, 2011)

Hi,

I would like to know the difference between a Muncie M20 from a Muncie M21 4-speed transmission.

I mainly need to know whether seals between these two gearboxes are interchangeable.


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## orelog (Dec 21, 2011)

The only difference is the gear ratio and the ratio spread between the gears. All seals and gaskets will interchange.


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## extinctmake (Feb 8, 2011)

Good. I wanted to make sure the seal kit I buy will work. I know I have a Muncie in my car, but I wasn't sure if it's a M20 or M21. I think it's a M21. My car had the original 3-speed replaced with a 4-speed long before I got it.

How tough is it to put the side cover back on when removing to replace shift shaft seals? I know the shifter has to come off, but I was wondering if there's a trick to getting the shift forks back in during re-assembly.


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## orelog (Dec 21, 2011)

Here is a link for a total rebuild of a muncie 4-speed. http://www.lbfun.com/warehouse/tech_info/transmission, shifter, clutch & rear/muncie.pdf


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