C2 Rear End Code (Ratio/date)

[Ken K.]

This is the code I found on my rear end. (My '66 rear end) It does not seem correct or to be similar to the other 1966 rear end codes I see. Can anyone break down the code and let me know the ratio and date.
The code is: AA W 306 E1
Thanks

[John H.]

Re: C2 Rear End Code (Ratio/date)

Ken -

The "AA" code was used from '71-'75 for a 3.55 axle, with the julian date coding format you showed (306th day of the year), Eaton Posi, first shift.

You'll find the casting number for the diff housing on the passenger side, above the horizontal "fin" on the housing - 66's used #3876476N, and '67-'75 used #3899143. The casting date code is on the driver's side, partially obscured behind the front of the camber strut bracket; that will tell you what year the diff was cast.