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

Prefix Axle Ratio
CA 3.08:1
CB 3.36:1
CC 3.73:1
CD 3.07:1 ~ Positraction
CE 3.08:1 ~ Positraction
*CF *3.31:1 ~ Positraction
CG 3.36:1 ~ Positraction
CH 2.73:1 ~ Positraction
CI 3.73:1 ~ Positraction
CJ 3.07:1
CK 3.07:1
CL 2.73:1
CM 2.73:1 ~ Positraction
CN 3.31:1
CO 3.31:1 ~ Positraction
CP 2.73:1
CQ 2.56:1
CR 3.70:1 ~ Positraction
CS 2.56:1
CT 3.73:1
CU 3.73:1 ~ Positraction w/Metallic Brakes
CV 3.70:1
CW 3.31:1
CX 3.07:1
CY 3.07:1
CZ 2.73:1
FH 2.73:1 ~ small ring gear (Note 1)
FI 2.73:1 ~ Positraction, small ring gear (Note 1)
FJ 3.08:1
FK 3.08:1 ~ Positraction
FL 3.36:1
FM 3.36:1 ~ Positraction
FN 3.55:1 ~ small ring gear (Note 1)
FO 3.55:1 ~ Positraction, small ring gear (Note 1)
FP 3.70:1
FQ 3.70:1 ~ Positraction
K2 3.55:1
K3 3.55:1 ~ Positraction
K4 3.73:1
K5 3.73:1 ~ Positraction
K6 4.10:1 ~ Positraction
K7 4.56:1 ~ Positraction
K8 4.88:1 ~ Positraction
KA 3.55:1 ~ small ring gear (Note 1)
KB 3.55:1 ~ Positraction, small ring gear (Note 1)
KC 2.73:1 ~ Positraction, small ring gear (Note 1)
KD 2.73:1 ~ large ring gear (Note 1)
KE 2.56:1 ~ Positraction
KF 3.55:1 ~ Positraction, large ring gear (Note 1)
KG 3.55:1 ~ Positraction
KH 3.55:1
KI 2.56:1
KJ 3.55:1 ~ large ring gear (Note 1)
KK 4.10:1 ~ Positraction
KL 4.10:1 ~ Positraction
KM 4.56:1 ~ Positraction
KN 4.56:1 ~ Positraction
KO 4.88:1 ~ Positraction
KP 4.88:1 ~ Positraction
KQ 2.73:1
KR 2.73:1 ~ Positraction
KS 3.07:1
KT 3.07:1 ~ Positraction
KU 3.31:1
KV 3.31:1 ~ Positraction
KW 2.73:1 ~ w/Metallic Brakes
KX 3.07:1 ~ Positraction
KY 3.31:1 ~ Positraction
KZ 3.31:1

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
Number Month Number Month
01 January 02 February
03 March 04 April
05 May 06 June
*07 *July 08 August
09 September 10 October
11 November 12 December

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

Rear Axle Assembly Plant - 5th letter

Code Assembly Plant
*B *Buffalo, NY
G Chevrolet Gear & Axle
W Warren, MI
K McKinnon Industries