Chevelle Rear Axle & Differential Identification
Decoding Differential Casting Numbers
The differential casting number can be found in the webbing area surrounding the backside of the carrier housing next to the left or right axle tube. You should also find a date code casting in the webbing area, consisting of a letter and two to three numbers.
For example: E 21 7 decodes this way: E / 21 / 7
- First letter indicates the month of production, E is for May.
- Second and/or third number indicates the day of production, 21 is for the 21st day.
- The last number indicates the year of production, 7 is for 1967.
| Code | Month | Code | Month | Code | Month | Code | Month |
|---|---|---|---|---|---|---|---|
| A | January | D | April | G | July | J | October |
| B | February | E | May | H | August | K | November |
| C | March | F | June | I | September | L | December |
Match up the differential casting number with the year decoded from the date code casting. Select the year to proceed with decoding the differential identification codes.
| 10 Bolt Housings | |
|---|---|
| Casting | Year |
| 3839390N | 1964 |
| 3959139N | 1965 |
| 3875744N | 1966 |
| 3894938NF | 1967 |
| 3917123NF | 1968 |
| 3859037NF | 1969 |
| 3969277NF | 1970 |
| 3969277NF | 1971 |
| 3969277NF | 1972 |
| 12 Bolt Housings | |
|---|---|
| Casting | Year |
| 3859140N | 1965 |
| 3875745N | 1966 |
| 3894939NF | 1967 (Early) |
| 3917124NF | 1967 (Late) |
| 3917124NF | 1968 |
| 3917124NF | 1969 (Early) |
| 3959038NF | 1969 (Late) |
| 3969278NF | 1970 |
| 3969278NF | 1971 |
| 3969278NF | 1972 |