1966 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
3875744N 1966
12 Bolt Housings
Casting Year
3875745N 1966

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: CI0219B decodes this way: CI / 02 / 19 / 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 3.70 Metallic Brakes
CI 3.73 Positraction
CJ 3.07 Metallic Brakes
CK 3.07 Positraction w/ Metallic Brakes
CL 3.08 Metallic Brakes
CM 3.08 Positraction w/ Metallic Brakes
CN 3.31 Metallic Brakes
CO 3.31 Positraction w/ Metallic Brakes
CP 3.36 Metallic Brakes
CQ 3.36 Positraction w/ Metallic Brakes
CR 3.70 Positraction
CS 3.70 Positraction w/ Metallic Brakes
CT 3.73 Metallic Brakes
CU 3.73 Positraction w/ Metallic Brakes
CV 3.70 Overdrive
CW 3.31  
CX 3.07  
KC 2.73 Metallic Brakes
KD 2.73 Positraction
KE 2.73 Positraction w/ Metallic Brakes
KF 3.55 Metallic Brakes
KG 3.55 Positraction w/ Metallic Brakes
KH 3.55 Positraction
KI 2.73 "396" w/ Powerglide
KJ 3.55  
KK 4.10 Positraction
KL 4.10 Metallic Brakes
KM 4.56 Positraction
KN 4.56 Metallic Brakes
KO 4.88 Positraction
KP 4.88 Metallic Brakes
Code Assembly Plant
B Buffalo, NY
G Chevrolet Gear & Axle
W Warren, MI
K McKinnon Industries