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.

CX = 3.07:1
1028 = October, 28
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
CF3.31:1 ~ Positraction
CG3.36:1 ~ Positraction
CH2.73:1 ~ Positraction
CI3.73:1 ~ Positraction
CJ2.56:1
CK2.56:1 ~ Positraction
CL2.56:1
CM2.56:1 ~ Positraction
CN2.56:1
CO2.56:1 ~ Positraction
CP2.73:1
CQ2.56:1
CS2.56:1 ~ Positraction
CT2.73:1
CW3.31:1
*CX*3.07:1
CY3.07:1
CZ2.73:1
KA3.55:1 ~ small ring gear (Note 1)
KB2.56:1 ~ Positraction, small ring gear (Note 1)
KC2.73:1 ~ Positraction, small ring gear (Note 1)
KD2.73:1 large ring gear (Note 1) (Note 1)
KE2.73:1 ~ Positraction, small ring gear (Note 1)
KF3.55:1 ~ Positraction, large ring gear (Note 1)
KG3.08:1 ~ small ring gear (Note 1)
KH3.08:1 ~ Positraction, small ring gear (Note 1)
KI3.36:1
KJ3.55:1 ~ large ring gear (Note 1)
KK4.10:1 ~ Positraction
KL3.36:1 ~ Positraction, small ring gear (Note 1)
KM4.56:1 ~ Positraction
KN3.55:1 ~ small ring gear (Note 1)
KO4.88:1 ~ Positraction
KP3.55:1 ~ Positraction, small ring gear (Note 1)
KQ4.10:1 ~ Positraction, heavy duty
KX3.07:1 ~ Positraction
FH2.73:1
FI2.73:1 ~ Positraction
FJ3.08:1
FK3.08:1 ~ Positraction
FL3.36:1
FM3.36:1 ~ Positraction
FN3.55:1
FO3.55:1 ~ Positraction

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
07July08August
09September*10*October
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