1968 Chevelle Rear Axle & Differential Identification

Picture of a rear differential

Casting Numbers

These are the casting numbers used during this production year. If they were used during another year, you will find the additional years listed below.

10 Bolt Housings
Casting Year
3917123NF 1968
12 Bolt Housings
Casting Year
3917124NF 1967 (Late)
3917124NF 1968
3917124NF 1969 (Early)

Decoding Rear Axle Codes

The rear axle identification code is stamped on the axle housing on the bottom, front left, or front right axle tube next to the carrier housing or about 8 to 12 inches from the backing plates. This code consists of 7 digits and characters indicating the stock gear ratio, month/day of assembly, and the assembly plant. Sometimes you will find an extra character stamped near this code, E indicates Eaton positraction.

For example: FK0521B decodes this way: FK / 05 / 21 / B.

Code Gear Ratio Notes
CA 3.08  
CB 3.36  
CC 3.73  
CD 3.07 Positraction
CE 3.08 Positraction
CF 3.31 Positraction
CG 3.36 Positraction
CH 2.73 Positraction
CI 3.73 Positraction
CJ 3.08  
CP 2.73  
CR 3.70 Positraction
CU 3.73 Positraction w/ Metallic Brakes
CV 3.70  
CW 3.31  
CX 3.07  
CY 3.07  
CZ 2.73  
FH 2.73 Small Ring Gear
FI 2.73 Positraction - Small Ring Gear
FJ 3.08  
FK 3.08 Positraction
FL 3.36  
FM 3.36 Positraction
FN 3.55 Small Ring Gear
FO 3.55 Positraction - Small Ring Gear
FP 3.70  
K2 3.55  
K3 3.55 Positraction
K4 3.73  
K5 3.73 Positraction
K6 4.10 Positraction
K7 4.56 Positraction
K8 4.88 Positraction
KA 3.55 Small Ring Gear
KB 3.55 Positraction - Small Ring Gear
KC 2.73 Positraction - Small Ring Gear
KD 2.73 Large Ring Gear
KF 3.55 Positraction - Large Ring Gear
KJ 3.55 Large Ring Gear
KK 4.10 Positraction
KM 4.56 Positraction
KN 4.56 Positraction
KO 4.88 Positraction
KW 2.73 Metallic Brakes
KX 3.07 Positraction
KY 3.31 Positraction
KZ 3.31  
Code Assembly Plant
B Buffalo, NY
G Chevrolet Gear & Axle
W Warren, MI
K McKinnon Industries