1964 or 1974 rear diff casting?

[Tom Dingman (4889)]

The date/ratio code for the rear diff. (rear pumpkin) installed in my 1966 Corvette is stamped A O W 254 E1 - The casting appears to be H304. This looks more like a 74 rear to me, but A 0 is not a ratio code for 1974, or 1964 for that matter (Colvin). I've seen 63 and 66 rears with month day year instead. Does anyone know when the change to this style rear codes was made?

Same car has a paper part number tag on the bracket that holds this rear diff. from the front. It's been there since 1978, but I don't think it's a factory part. Comments? THANKS - td

[John Hinckley (29964)]

Re: 1964 or 1974 rear diff casting?

Tom -

May be a service replacement - the Julian assembly date (254) and the August 30th casting date make sense together, and 1971 and later axles used the Julian date coding. Production diff brackets didn't have any paper tags/labels on them, but service parts did.

[Tom Dingman (4889)]

Re: 1964 or 1974 rear diff casting?

Thanks John!

[Joe Lucia (12484)]

Re: 1964 or 1974 rear diff casting?

Tom------

Another easy thing to check for is the carrier housing casting number. For 1964, the casting number will be 3818753. The 1974 carrier housing will have casting number 3899143.

[Tom Dingman (4889)]

Re: 1964 or 1974 rear diff casting?

Thanks Joe!