| 1969 Muncie P9C15A ~ March 15, 1969 - M20 1970 P0R23A ~ M20 dated October 23, 1969 P0R29A ~ M20 dated October 29, 1969. The Hurst Competition Plus Shifter fits both with and without console.If using a Hurst Super Shifter on a Muncie there is only one shifter and one installation kit.The shifter is #3917535 and the installation kit is #3738616. Easily identified by the reverse gear being on the main case instead of the tail housing.
Another misconception is if you have a drain plug you have a M22.
This was only true when the first M22 boxes were created; all 3925661 castings (1970-1974) had drain plugs.
All 26 spline inputs came with 32 spline output shafts and all 10 spline inputs came with 27 spline output shafts.
It is commonly mistaken that all "fine spline" 26 spline input shafts are M22 transmissions.
Partial or "concealed/confidential" VIN Stamping Most transmissions since 1962 will also have a CON VIN (concealed or confidential VIN, partial VIN, or VIN derivative - whichever term one likes) stamped in the case generally along the top ridge or even on a mounting surface such as the flange mounting the tail shaft to the main case noting the original car it was installed in.
The stamped CON VIN is the same that is stamped on the engine pad in all 1968 and later Chevelles, and generally 1966 & 1967 SS396 Chevelles with an alphanumeric set of characters like 7K123456; model year, assembly plant, and vehicle sequence number.
If anyone as documented proof, such as a warranty card (Protect-O-Plate) showing a Saginaw coded M20 (R) prior to February/March of 1966 is encouraged to send a readable image of the warranty card for verification.
The M20 and M21 have the same cut to the gears, the M22 is a straighter cut resulting in a greater strength.
Note that a Muncie dated with a September to December build date was actually built the prior calendar year.
An example would be the date code P8T13, meaning 1968 (8), December (T), 13th.
From 1963 to 1965 the close ratio M21 was ordered under the M20 RPO code and the factory decided whether to install a wide ratio M20 or close ratio M21 depending on the rear axle ratio specified.