SM420 Identification

[akeane01]

I bought a 4 speed SM420 transmission without knowing the year but had some idea. I found out thru other postings that a 7 digit casting number beginning with 37,38 or 39 fall in the 1964-67 year time frame. You could also tell the year by the code above the casting number. For ex: B1060 means it was feb 10, 1960.. I thought I was all set to identify any SM420 but what i have seen in looking at SM420's is that there are some that have the 1st letter followed by only 3 numbers instead of 4. Mine is L184..

So does anyone know how to decode this to figure out what year this is?

here is a picture..

thanks

[OrrieG]

I'm guessing November 18, 1964. I have a 64 Chevelle and all the date codes are a similar configuration, only the last digit for the year. The letter is the month A-M, note that "I" is not used to avoid confusion with the number 1. If there was another number after the "4" and off set a little it would indicate the shift.

[dwcsr]

Dec 18th 1964 C60 w/ a 292 or 250 6cyl.

[terrybrown95919]

As an aside, and not to high jack the thread.... I do have a truck SM420 with new bearings and no miles after installation. If interested, email me: terrybrown95919@yahoo.com (adapters for both open and closed drive lines)