A/T - Understanding Identification Information

Number: 86-51

Section: 7

Date: Feb. 1986
Subject: ALL THM TRANSMISSIONS-IDENTIFICATION INFORMATION, INCLUDING 3-LETTER MODEL CODE

MODEL AND YEAR: ALL MODELS

TO: ALL CHEVROLET DEALERS

This information is intended to assist field technicians in understanding the transmission identification (I.D.), its meaning, and where it is located on currently manufactured THM automatic transmissions.

The transmission identification tag or stamped identification contains such information as transmission type, model year, model, serial number, and Julian date.

Refer to the following information and illustrations which will help explain all transmission identifications:

EXPLANATION OF ALL KEY TRANSMISSION IDENTIFICATIONS

MODEL YEAR: Tells what model year the transmission was built.

MODEL: Beginning with the start of 1986 production, all THM transmissions will have a 3-letter model designator as opposed to the 2-letter model designator used in previous years. The third letter in each code group will identify the type of transmission as follows:

TYPE OF THIRD LETTER OF
TRANSMISSION CODE GROUP
25C C
180C* L
200C B
200-4R F
350C* R
400 A
440-T4 H
700-R4 M

* Does not carry 3-letter model designation on nameplate.
JULIAN DATE: Tells what day of the year the transmission was built. It is also important to remember that the transmission model year starts MID YEAR. This means the first transmission built in any model year will start with a higher Julian date.

EXAMPLE: IF THE FIRST TRANSMISSION IN 1986 WAS BUILT ON AUG. 5, THEN THE JULIAN DATE STARTS AT 217 AND GOES TO 365 (DECEMBER 31). THE JULIAN DATE WILL THEN DROP TO 001 (JANUARY 1) AND CONTINUE TO 216 (AUGUST 4, 1987).

SERIAL NUMBER; Tells what sequence the transmission was built.

SHIFT BUILT: Tells what shift the transmission was built.