1969 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 font of right axle tube either adjacent to the carrier housing or about 8" - 10" inboard from the backing plates. The particular engine RPO code is listed in parentheses as found on build sheets.

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)

Casting Numbers:
12-Bolt Casting #3917124 (early model year), #3959038NF (late model year)
10-Bolt Casting #3859037NF

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 ~ 10-bolt (L14/307)*
CB 3.36:1 ~ 10-bolt
CC 3.73:1 ~ 12-bolt
CD 3.07:1 ~ 12-bolt Positraction
CE 3.08:1 ~ 10-bolt Positraction
CF 3.31:1 ~ 12-bolt Positraction (L34/396)*
CG 3.36:1 ~ 10-bolt Positraction
CH 2.73:1 ~ Positraction
CI 3.73:1 ~ 12-bolt Positraction (L34/396 & L78/396)*
CJ 2.56:1
CK 2.56:1 ~ Positraction
CL 2.56:1 ~ 10-bolt (L65/350-2)*
CM 2.56:1 ~ Positraction
CN 2.56:1 ~ 12-bolt (L48/350-4)*
CO 2.56:1 ~ Positraction
CP 2.73:1 ~ 10-bolt (L14/307)*
CQ 2.56:1 ~ 10-bolt (L65/350-2)*
CS 2.56:1 ~ Positraction
CT 2.73:1
CW 3.31:1 (L35/396, L34/396 & L48/350-4)*
CX 3.07:1 ~ 12-bolt (L35/396)*
CY 3.07:1 ~ 12-bolt
CZ 2.73:1
FH 2.73:1
FI 2.73:1 ~ Positraction
FJ 3.08:1 ~ 12-bolt
FK 3.08:1 ~ 12-bolt Positraction
FL 3.36:1 ~ 10-bolt
FM 3.36:1 ~ 10-bolt Positraction
FN 3.55:1
FO 3.55:1 ~ Positraction
KA 3.55:1 small ring gear
KB 3.55:1 ~ Positraction, small ring gear
KC 2.73:1 ~ Positraction, small ring gear
KD 2.73:1 ~ 12-bolt large ring gear (L48/350, L35/396)*
KE 2.73:1 ~ Positraction, small ring gear
KF 3.55:1 ~ 12-bolt Positraction, large ring gear (L35/396 & L34/396)*
KG 3.08:1 ~ 12-bolt small ring gear
KH 3.08:1 ~ 12-bolt Positraction, small ring gear
KI 3.36:1 ~ 10-bolt
KJ 3.55:1 large ring gear
KK 4.10:1 ~ 12-boltPositraction (L78/396)*
KL 3.36:1 ~ Positraction, small ring gear
KM 4.56:1 ~ 12-bolt Positraction
KN 3.55:1 small ring gear
KO 4.88:1 ~ 12-boltPositraction
KP 3.55:1 ~ Positraction, small ring gear
KQ 4.10:1 ~ 12-bolt Positraction, heavy duty (COPO)*
KX 3.07:1 ~ 12-bolt ~ Positraction
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

* Engine RPO code and size following the rear axle ratio are taken from build sheets, protect-o-plate warranty cards, or known engine/rear end combinations and may not reflect the only engine the rear axle codes came with. Where there are no RPO/engine information following the rear axle code only means I do not have documentation to verify them.

File Photo
KD 2.73:1 ~ 12-bolt large ring gear, October 30, Buffalo, NY

File Photo
KF 3.55:1 ~ 12-bolt Positraction, large ring gear February 14, Buffalo, NY

Courtesy Sam Aston
KF 3.55:1 ~ 12-bolt Positraction, large ring gear June 5, McKinnon Industries

Casting Date Examples

File Photo
Casting date example of C 21 9 for March 21, 1969

Courtesy Pete and Wayne Jennings
Casting date example of D 16 9 for April 16, 1969
Courtesy Pete and Wayne Jennings

File Photo
Casting date example of F 2 9 for June 2, 1969

Casting Numbers Examples

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1967-1969 ~ Variations of casting number 3917124

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1969 ~ 3959038NF and X3959038NF