Passenger Car Transmission Production Code Explanation
Manual TransmissionsFour-speed transmissions built at Chevrolet plants will carry a production code number. The code number identifies the source, model year, month and day produced.
The transmission codes are located as follows:
Four-Speed
The Muncie (cast iron case) transmission (Saginaw type) is stamped on the machined surface of the left side of the case just below the side cover.
The Muncie 70mm (aluminum case) transmission is stamped on the bottom center front of case.
EXAMPLE:
K 4 R 03
MODEL MONTH DAY
SOURCE CODE YEAR PRODUCED PRODUCED
A-January B-February C-March
K=Muncie (Chevette, 70MM D-April
4-Speed) E-May
H-June
R=Muncie (Passenger 4-Speed K-July
Saginaw Type) M-August
P-September R-October S-November T-December
Warner Gear Four and Five Speed Manual Transmissions
The manual transmission code, part number and serial number, appears on a metal tag attached to an extension housing bolt on the left side (8 o'clock position).
EXAMPLE TAG:
Customer P/N 14078525 WA2041 Source Code
Source P/N 13-52-062 21975 Sequential
Serial Number
EXAMPLE
W A 20 4 1
SHIFT
SOURCE CODE MONTH DAY YEAR CODE
W = Warner A-Jan. G-July 20=20th 4 = Shift
B-Feb. H-Aug. Day 1984 Produced
C-Mar. J-Sept.
D-Apr. K-Oct.
E-May L-Nov.
F-June M-Dec.
Four-Speed Manual With Automatic Overdrive (Doug Nash) MK2
Source trademark appears above speedo gear opening.
The Doug Nash transmissions have the source code, model year, unit serial number and ratio identification stamped on two (2) metal tags. One (1) tag is attached to the T-10 transmission side cover lower bolt, and the other tag is on the overdrive pan front bolt.
PASSENGER CAR TRANSMISSION PRODUCTION CODE EXPLANATION:
EXAMPLE: D 4 C 25 037 - CD
D 4 C 25 037 C D
SOURCE CODE YEAR MONTH DAY SERIAL NUMBER RATIO P/N
D=Doug Nash 4=1984 A=Jan. 25=25th 37=37th Unit
B=Feb. Day Built
C=Mar. D=Apr. E=May F=June G=July H=Aug. J=Sept. K=Oct. L=Nov. M=Dec.
The tag on the T-10 transmission has an additional code.
Chevette Five Speed Isuzu Transmission:
Chevette Five Speed Isuzu Transmission
Right side of transmission case at rear extension is a six digit ink stamp transmission serial number. On right side of bell housing at approximately 4:00 o'clock position, five digit ink stamp.
Five Speed Isuzu Manual Transaxle:
Five Speed Isuzu Manual Transaxle (MY7)
On fifth gear cover ten digit die stamped number.
Automatic Transmissions
THM 180C Automatic Transmission
The THM 180C automatic transmission code and transmission serial number appears on a metal tag fastened to the left side of the transmission just rearward of the converter housing.
THM 200C Automatic Transmission
The identification tag is located on the right side of the transmission case and includes the model year, application code and sequence number.
EXAMPLE:
84 OU 6991
Model Year Vehicle Sequence Number
Application Code
THM 200-4R Automatic Transmission
The identification tag is located on the right side of the transmission case and includes the model year, application code, build date code and the sequence number.
EXAMPLE:
84 BY 201 0346
Model Year Vehicle Application Build Date Sequence
Code Code Number
THM 250C and 350C Automatic Transmissions
THM 250C and 350C transmissions produced by Chevrolet Parma have the production code stamped on the governor cover.
EXAMPLE
B 4 D 10 D
MODEL MONTH DAY SHIFT
SOURCE CODE YEAR PRODUCED PRODUCED PRODUCED
B = Parma (THM 250C) 1984 A = Jan. 10th Day D = 1st
B = Parma (THM 350C) B = Feb. N = 2nd
C = March
D = April
E = May
H = June
K = July
M = Aug. P = Sept. R = Oct. S = Nov. T = Dec.
THM 440-T4 Four Speed Automatic
The code is located on a stamped metal tag on the rear face of the transaxle case adjacent to right hand axle opening.
Identification Tag:
An example of the identification tag is shown below:
THM 700-4R Automatic Transmission
The identification number is stamped into right rear oil pan rail. The format includes the year, model, Julian build date and shift.
EXAMPLE
4 YA 222 D
MODEL JULIAN
YEAR NO. BUILD DATE SHIFT
D = Day N = Night
PASSENGER CAR TRANSMISSION IDENTIFICATION NUMBER FOR "SERVICE" USAGE
The following system will be used to identify service transmission assemblies. This number system applies to domestically produced complete service transmission assemblies only. Transmission cases are no longer identified. Manufacturing plants will number each service assembly as it is produced. The first letter will designate the GM division which produced the unit - "C" (Chevrolet). The second letter will indicate the type of unit "T" (transmission). The number following the letter will designate the model year - "4" (1984). The last five digits specify the service replacement sequence number. The group of numbers to be used by Chevrolet Manufacturing plants are as follows:
PLANT SERIAL SEQUENCE
Chevrolet - Parma Transmission Plant 00001 to 14999
Chevrolet - Muncie Transmission Plant 25000 to 44999
EXAMPLE: Number CT400175 designates Chevrolet transmission, year and 175th unit produced for service at Parma.
Upon completion of the serial sequence, the plant will reuse the above numbers using a letter prefix, such as A, B and C.
EXAMPLE: CT4A00175
Hydra-Matic Division 00001 to 99999
Hydra-Matic Division transmissions will be numbered with the letter "H" regardless of the GM division using the transmission.
1984 PASSENGER CAR TRANSMISSION PROGRAM SUMMARY
PROCESSING NUMBER
MANUAL 4-SPEED
MK2 2.88:1 First Gear Ratio - Automatic Overdrive Doug Nash
M17 3.31:1 First Gear Ratio, Transverse Muncie
M26* 3.50:1 First Gear Ratio Muncie
M19 3.53:1 First Gear Ratio, Transverse Muncie
MY8 3.53:1 First Gear Ratio, Transverse Muncie
MY1 3.75:1 First Gear Ratio Muncie
MANUAL 5-SPEED
MK4 3.50:1 First Gear Ratio Borg Warner
MK6 2.95:1 First Gear Ratio Borg Warner
MK5 3.50:1 First Gear Ratio Borg Warner
MB4 3.76:1 First Gear Ratio Borg Warner
M75 3.79:1 First Gear Ratio Isuzu
MY7 3.91:1 First Gear Ratio, Transverse Isuzu
AUTOMATIC 3-SPEED
MD9 125c, Converter Clutch, Transverse Willow Run - Hydra-matic
MD2 180c, Converter Clutch Strausbourg
MV9 200c, Converter Clutch Willow Run - Hydra-matic
M31 250c, Converter Clutch Parma
MV4 350c, Converter Clutch Parma
AUTOMATIC 4-SPEED
MW9 200-4R, Converter Clutch and Overdrive 3 Rivers - Hydra-matic
ME9 440-T4, Converter Clutch and Overdrive, Transverse Warren - Hydra-matic
MD8 700-R4, Converter Clutch and Overdrive Toledo - Hydra-matic