m22 how to tell from m21?

[wheelhop]

I called a buddy out in California who rebuilds these all the time and here's what he told me, please excuse me in advance if something was lost in the translation:

On 1966 and newer muncie transmissions, the input shaft on a M-22 did not have a ring around it. M-21's had 1 ring, M-20's had 2 rings. This is of course is assuming the input shaft is original to the trans.

On the passenger side of the main case of the trans, there should be a C-code somewhere near the v.i.n..

Inside of the trans, the gears are cut at a straighter angle.

M-22's could have been fine or course splined.
The fine splined ones were produced between 1971 and 1974

any questions or need help rebuilding your trans call Craig Wright of "The Wright Connection" @ 661-304-1967