Could someone help me to identify which of the muncie transmissions I have in my car, the casting number is 3857584g, its in a 66 f85.

Thank you,
Jeremy

 

the best way is to take the side cover off to look at the cut and count of the teeth. several years ago i got one that had M-21 markings on the case but when i got it home i found that someone put M-20 guts in it. i found the same thing in a parts car i had in the 90s. that one i got lucky on. the case was marked as an M-20 and had M-22 guts in it. i think to many people busted them and pieced parts together over the years to trust the outside markings. it has been several years since i looked at 4 speed numbers but i don't think that is the right number to determine what it originally was.

 

3857584 = 1966 – 1970 Passenger side speedo, 27 spline and is a tailhousing casting #
This info here....
http://www.5speeds.com/casting.html
More info here....
http://www.5speeds.com/muncie2.htm