Truck Transmission Production Code Explanation
Muncie Manual Transmission Production Code ExplanationThe production code number contains the source code, model year and build date.
EXAMPLE:
N 4 D 10
SOURCE CODE MODEL YEAR BUILD MONTH DAY CODE
S - 3 Speed 1984 A - Jan. 10th
(Saginaw Type) B - Feb.
C - March
N - 4 Speed D - April
(117mm) E - May
H - June K - July M - Aug. P - Sept. R - Oct. S - Nov. T - Dec.
3 Speed (Saginaw Type)
The code is stamped on the left side of the case just below the side cover.
Muncie Truck 4 Speed
Stamped on the rear face of the transmission case just below the rear retainer.
New Process 205, 207 and 208 Model 4-Wheel Drive Transfer Case
The build date showing the month, day and year along with the Chevrolet part number is on a metal tag attached to the front face of the transfer case at PTO cover.
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.
Truck Four-Speed Isuzu Transmission (77.5 mm):
Truck Four-Speed Isuzu Transmission (77.5 mm)
Right side of bell housing at 3:00 o'clock position five digit ink stamp transmission serial number. Below serial number is five digit date stamp.
350C and 700-R4 Turbo Hydra-Matic Transmissions
Refer to the passenger section of this bulletin for production code explanations.
400-475 Model Turbo Hydra-Matic Transmission
The transmission model number and sequence number is stamped on the identification plate located at the right rear extension.
MODEL AND SEQUENCE NUMBER EXAMPLE:
TRUCK TRANSMISSION IDENTIFICATION NUMBER FOR "SERVICE" USAGE
The following system will be used to identify service transmission assemblies domestically produced. This number system applies to 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 99999
Hydra-Matic 00001 to 99999
Hydra-Matic transmissions will be numbered with the letter "H" regardless of the GM division using the transmission.
EXAMPLE: Number CT400175 designates Chevrolet transmission, year and 175th unit produced for service at Parma.
Upon completion of the serial sequence, the plant will re-use the above numbers using a letter prefix, such as A, B or C to indicate late production transmission; for example: CT2A0001.
1984 TRUCK TRANSMISSION PROGRAM SUMMARY
PROCESSING NUMBER
MANUAL 3-SPEED
M62 2.85 = 1 First Gear Ratio Muncie
M64 3.50 = 1 First Gear Ratio Muncie
MANUAL 4-SPEED
MY6 3.09:1 First Gear Ratio, Overdrive New Process
M20 6.55:1 First Gear Ratio Muncie
M73 4.09:1 First Gear Ratio Isuzu
M77 4.07:1 First Gear Ratio Borg Warner
MANUAL 5-SPEED
MB1 4.03:1 First Gear Ratio, Overdrive Borg Warner
MB6 4.03:1 First Gear Ratio, Overdrive Borg Warner
AUTOMATIC 3-SPEED
MV9 200C, Converter Clutch Willow Run - Hydra-matic
MV4 350C, Converter Clutch Parma
M40 400 Willow Run - Hydra-matic
M40 475 Willow Run - Hydra-matic
AUTOMATIC 4-SPEED
MD8 700-R4, Converter Clutch, Overdrive Toledo - Hydra-matic