Transmissions can be identified by three different codes.
- Source Serial Number Code
(Automatic & Manual)
- These codes were stamped on the left side near the top forward of the housing.
- Manual transmissions were stamped on the case.
- Model Identification Code
(Automatic)
- These codes were stamped on a metal tag located on the right side of the transmission.
Exceptions are : 1965 stamped them either on a metal tag or the low servo cover.
1966 were stamped on the low servo cover.
- Production Code Number
(Manual)
- These codes were stamped on the right side of the transmission case ahead of the extension.
Exception : 1964 were stamped on the left side of the case rear of the cover.
I covered Source Serial Number Code and Model Identification Code but not Production Code Number. These still should give you enough information to check the transmission installed.
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1. Source Serial Number Code
(Automatic & Manual)
- From 1964-66 transmissions carried a source serial number, which consisted of a plant prefix letter, a production date and a day/night shift suffix.
Example: R315N=Muncie,4 Speed built on March 15 during the night shift.
- In 1967 the serial number was changed, it consisted of a plant prefix letter, year number, and month produced (with a letter code instead of a number).
| A-January |
B-February |
C-March |
| D-April |
E-May |
H-June |
| K-July |
M-August |
P-September |
| R-October |
S-November |
T-December |
Example: N7B27=Muncie,4 Speed built on February 27.
- On October 21, 1968, another letter code was added to the plant prefix number to identify Muncie transmission ratios.
Muncie 3 Speed: A=3.03:1
B=2.42:1
Muncie 4 Speed: A=2.52:1 Wide Range
B=2.2:1 Close Range
C=2.2:1 Rock Crusher.
- Beginning in 1968, the car's last eight numbers of the VIN were stamped on the transmission. As with all car productions there are exceptions to the rule. One good source has a late model 1967 GTO with the VIN stamped on it.
Source Serial Number Code/
Plant Prefix Letters
| Prefix |
Plant |
Transmission Type |
| A |
Cleveland |
Manual Powerglide |
| B |
Cleveland |
Turbo Hydra-Matic |
| C |
Cleveland |
Powerglide |
| CA |
Hydro-Matic |
Turbo Hydra-Matic |
| D |
Saginaw |
Overdrive |
| E |
McKinnon |
Powerglide |
| H |
Muncie |
3 Speed |
| K |
McKinnon |
3 Speed |
| L |
GM of Canada |
Turbo Hydra-Matic |
| M |
Muncie |
3 Speed & Overdrive |
| N |
Muncie |
4 Speed |
| O |
Saginaw |
Overdrive |
| P |
Warner Gear |
3 & 4 Speed |
| P |
Muncie |
4 Speed |
| R |
Muncie |
4 Speed |
| R |
Saginaw |
4 Speed |
| S |
Muncie |
3 Speed |
| S |
Saginaw |
3 Speed |
| T |
Toledo |
Powerglide |
| X |
Cleveland |
Turbo Hydra-Matic |
| Y |
Toledo |
Turbo Hydra-Matic |
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2. Model Identification Code
(Automatic)
1964
- 64=Model Year
- 30=V8 Engine Application
- 135=Built on the 135th day of the Year
1965
- 65=Model Year
- 40=GTO Application
- 135=Built on the 135th day of the Year
1966
- 66=Model Year
- NA=GTO Application
- 135=Built on the 135th day of the Year
1967
- 67=Model Year
- PT=400,2 barrel, Application
- 1234=Transmission Serial Number
Application Codes
- PT=400,2 barrel
- PS=400,4 barrel
- PQ=400,High Output/Ram Air
- PX=400,High Output/Ram Air
1968
- 68=Model Year
- PT=400,2 barrel, Application
- 1234=Transmission Serial Number
Application Codes
- PT=400,2 barrel
- PQ=400,Ram Air
- PX=400,All non-Ram Air/non-2 barrel
1969
- 69=Model Year
- PQ=400,Ram Air IV, Application
- 1234=Transmission Serial Number
Application Codes
- PT=400,2 barrel
- PQ=400,Ram Air IV
- PX=400,All non-Ram Air/non-2 barrel
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1970
- 70=Model Year
- PD=400,Ram Air III,Ram Air IV, Application
- 1234=Transmission Serial Number
Application Codes
- PD=400,Ram Air III,Ram Air IV
- PQ=400
- PR=455
1971
- 71=Model Year
- PY=400,4 barrel, Application
- 1234=Transmission Serial Number
Application Codes
- PQ=455,High Output
- PR=455,4 barrel
- PT=400,2 barrel
- PW=455,4 barrel
- PX=400,4 barrel
- PY=400,4 barrel
1972
- 72=Model Year
- PG=400,4 barrel, Application
- 1234=Transmission Serial Number
Application Codes
- PG=400,4 barrel
- PQ=455,High Output
- PR=455,4 barrel
- PT=400,2 barrel
1973
- 73=Model Year
- PT=400, Application
- 1234=Transmission Serial Number
Application Codes
- PT=400,4 barrel
- PQ=455,High Output
- PR=455,4 barrel
1974
- 74=Model Year
- ME=350, Application
- 1234=Transmission Serial Number
Application Codes
- ME=350,2 & 4 barrel
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D & L Transmission**For more information on all types of Parts and Service for Classic and Current Musclecar Manual Transmissions check out this site. Look up part numbers also.
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