GTO Transmissions

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Vehicle Specs

GTO Transmissions

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.

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

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

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

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.