1966 Chevelle Rear Axle Identification

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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.

Example: CG1025B decodes to CG ~ 3.36:1 Positraction, 1025 ~ Month [Oct] and Day [25], B ~ Buffalo (G=Chevrolet Gear & Axle, W=Warren, K=McKinnon Industries). See bottom of page for photo examples.

Casting Numbers:
12-Bolt Casting #3875745N
10-Bolt Casting #3875744N

The casting numbers/letters on rear end housings may have either a prefix or suffix of "N" or "NF" and no reason has been found yet why they may have one or the other.

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	3.70:1 ~ w/ Metallic Brakes
CI	3.73:1 ~ Positraction
CJ	3.07:1 ~ w/Metallic Brakes
CK	3.07:1 ~ Positraction w/Metallic Brakes
CL	3.08:1 ~ w/Metallic Brakes
CM	3.08:1 ~ Positraction w/Metallic Brakes
CN	3.31:1 ~ w/Metallic Brakes
CO	3.31:1 ~ Positraction w/Metallic Brakes
CP	3.36:1 ~ w/Metallic Brakes
CQ	3.36:1 ~ Positraction w/Metallic Brakes
CR	3.70:1 ~ Positraction
CS	3.70:1 ~ Positraction w/Metallic Brakes
CT	3.73:1 ~ w/Metallic Brakes
CU	3.73:1 ~ Positraction w/Metallic Brakes
CV	3.70:1 ~ Overdrive
CW	3.31:1
CX	3.07:1
KC*	2.73:1 ~ w/Metallic Brakes
KD*	2.73:1 ~ Positraction
KE*	2.73:1 ~ Positraction w/Metallic Brakes
KF	3.55:1 ~ w/Metallic Brakes
KG	3.55:1 ~ Positraction w/Metallic Brakes
KH	3.55:1 ~ Positraction
KI	2.73:1 ~ "396" w/Powerglide
KJ	3.55:1
KK	4.10:1 ~ Positraction
KL	4.10:1 ~ Positraction w/Metallic Brakes
KM	4.56:1 ~ Positraction
KN	4.56:1 ~ Positraction w/Metallic Brakes
KO	4.88:1 ~ Positraction
KP	4.88:1 ~ Positraction w/Metallic Brakes

* Not confirmed 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, N.Y.
G	Chevrolet Gear & Axle
W	Warren, MI.
K	McKinnon Industries

CW 1112 B decodes to CW=3.31:1, 1112=November 12, B is for Buffalo, N.Y.


CX 0727 B decodes to CX=3.07:1, 0727=July 27, B is for Buffalo, N.Y.

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