1966 Chevelle Rear Axle & Differential Identification
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.
- The first and second letters indicate the stock gear ratio. CI is a 3.73 positraction axle.
- The third and forth numbers indicate the month of production. 02 is for February.
- The fifth and sixth numbers indicate the day of production. 19 is for the 19th.
- The seventh letter indicates the assembly plant. B is for Buffalo, NY.
| 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 |