REAR AXLE IDENTIFICATION

The rear axle identification code consists of a two letter prefix indicating the gear ratio, four digits indicating the assembly date as month/day, and a single letter suffix indicating the manufacturing location. The identification code should be stamped on the bottom or front left or right axle tube either adjacent to the carrier housing or about 8" - 10" inboard from the backing plates.

CF = 3.31 Positraction
0706 = July 6
B = Buffalo, N.Y. manufacturing location

PrefixAxle Ratio
CA3.08:1
CB3.36:1
CC3.73:1
CD3.07:1 ~ Positraction
CE3.08:1 ~ Positraction
*CF*3.31:1 ~ Positraction
CG3.36:1 ~ Positraction
CH2.73:1 ~ Positraction
CI3.73:1 ~ Positraction
CJ3.07:1
CK3.07:1
CL2.73:1
CM2.73:1 ~ Positraction
CN3.31:1
CO3.31:1 ~ Positraction
CP2.73:1
CQ2.56:1
CR3.70:1 ~ Positraction
CS2.56:1
CT3.73:1
CU3.73:1 ~ Positraction w/Metallic Brakes
CV3.70:1
CW3.31:1
CX3.07:1
CY3.07:1
CZ2.73:1
FH2.73:1 ~ small ring gear (Note 1)
FI2.73:1 ~ Positraction, small ring gear (Note 1)
FJ3.08:1
FK3.08:1 ~ Positraction
FL3.36:1
FM3.36:1 ~ Positraction
FN3.55:1 ~ small ring gear (Note 1)
FO3.55:1 ~ Positraction, small ring gear (Note 1)
FP3.70:1
FQ3.70:1 ~ Positraction
K23.55:1
K33.55:1 ~ Positraction
K43.73:1
K53.73:1 ~ Positraction
K64.10:1 ~ Positraction
K74.56:1 ~ Positraction
K84.88:1 ~ Positraction
KA3.55:1 ~ small ring gear (Note 1)
KB3.55:1 ~ Positraction, small ring gear (Note 1)
KC2.73:1 ~ Positraction, small ring gear (Note 1)
KD2.73:1 ~ large ring gear (Note 1)
KE2.56:1 ~ Positraction
KF3.55:1 ~ Positraction, large ring gear (Note 1)
KG3.55:1 ~ Positraction
KH3.55:1
KI2.56:1
KJ3.55:1 ~ large ring gear (Note 1)
KK4.10:1 ~ Positraction
KL4.10:1 ~ Positraction
KM4.56:1 ~ Positraction
KN4.56:1 ~ Positraction
KO4.88:1 ~ Positraction
KP4.88:1 ~ Positraction
KQ2.73:1
KR2.73:1 ~ Positraction
KS3.07:1
KT3.07:1 ~ Positraction
KU3.31:1
KV3.31:1 ~ Positraction
KW2.73:1 ~ w/Metallic Brakes
KX3.07:1 ~ Positraction
KY3.31:1 ~ Positraction
KZ3.31:1

Note 1:
Just what constitutes a 'small' ring gear or 'large' ring gear is uncertain. My Chevrolet Parts and Accessories Catalog, circa 1972, only shows the gear ratio service part numbers so it is quite possible one or the other was discontinued in favor of a 'service' part. Anyone with knowledge of the differences, please contact me so I can share the information with all.

Assembly Month - 1st and 2nd numbers
NumberMonthNumberMonth
01January02February
03March04April
05May06June
*07*July08August
09September10October
11November12December

Assembly Day - 3rd and 4th numbers
01...31

Rear Axle Assembly Plant - 5th letter

CodeAssembly Plant
*B*Buffalo, NY
GChevrolet Gear & Axle
WWarren, MI
KMcKinnon Industries