70 Muncie tag, what does it indicate vs casting numbers?

Gary S

Administrator
Lifetime Gold Member
Apr 14, 1999
24,713
Bismarck, North Dakota
The metal tag has the actual GM part number on it. The tag on an M20 will be different from a tag for M21 or M22. The case casting numbers are the part numbers for just the case, not the complete tranny. For a given year, the M20, M21, and M22 would use the same case so would have the same number.
 

COPO

Veteran Member
Lifetime Gold Member
Sep 15, 1999
22,263
Ontario, Canada
4AB62FE7-E3F4-44D1-AE12-3A335CA1DC20.jpeg
 

clm69z28

Veteran Member
Oct 29, 2011
416
encinitas ca
From the Yenko website:

Muncie ID Tags
1964 M20 3841435
1965 M20 3857577
1965 M20 3857578 Z16
1966 M20 3870357 L-34 L-35
1966 M20 3890534 L-78
1966 M21 3877459 ALL
1966 M22 3879993 L-78
1967 M20 3870357 L-34 L-35 L-79
1967 M21 3877459 ALL
1967 M22 3879993 L-78
1968 M20 3915079 L-34 L-36 L-78 L-79
1968 M21 3915085 L-34 L-36 L-78 L-79
1968 M22 3925626 L-78
1969 M20 3950301 L-48 L-35
1969 M20 3946767 L-34 L-78
1969 M21 3946798 ALL
1969 M22 3950318 L-78 COPO L72
1970 M20 3952659 WB
1970 M21 3968012 (disc.3-11-70)
1970 M21 3968011 WL
1970 M22 3978766 WO
1971 M20 3974484 WN
1971 M22 3978766 WO
1972 M20 3974484 WN
1972 M22 6271517 WJ
 

l16pilot

Veteran Member
Lifetime Gold Member
Dec 13, 2004
2,277
Hurlock, MD, USA
From the Yenko website:

Muncie ID Tags
1964 M20 3841435
1965 M20 3857577
1965 M20 3857578 Z16
1966 M20 3870357 L-34 L-35
1966 M20 3890534 L-78
1966 M21 3877459 ALL
1966 M22 3879993 L-78
1967 M20 3870357 L-34 L-35 L-79
1967 M21 3877459 ALL
1967 M22 3879993 L-78
1968 M20 3915079 L-34 L-36 L-78 L-79
1968 M21 3915085 L-34 L-36 L-78 L-79
1968 M22 3925626 L-78
1969 M20 3950301 L-48 L-35
1969 M20 3946767 L-34 L-78
1969 M21 3946798 ALL
1969 M22 3950318 L-78 COPO L72
1970 M20 3952659 WB
1970 M21 3968012 (disc.3-11-70)
1970 M21 3968011 WL
1970 M22 3978766 WO
1971 M20 3974484 WN
1971 M22 3978766 WO
1972 M20 3974484 WN
1972 M22 6271517 WJ
Not completely correct. There were two distinct M22s in 1970. 3978766 WO was the large output tailshaft M22 as used in the Chevelles/El Caminos, etc. The M22 used in the 1970 Camaro was the small diameter output shaft and the PN tag reads 3968012 WM. (I know, weird it's the same number as the M21 discontinued in March 1970, but with the "WM" suffix added. This has been verified by an unrestored 22k original mile 70Z previously owned by Jack Seymour.
 




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