Chevelle Rear Axle & Differential Identification

Picture of a rear differential

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

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