Hi All, my '65 Coupe has a later model differential but after running through the archives, I don't seem to find the code listed. I bought the car in '85 and other than the original 300 horse 327, just about everything else had been messed with, and not in a good way. I wound up doing a body off, not because I wanted to but because it needed it. At the time, I saw an 'AT' on the diff and kinda remember checking the gears and finding it was a 3:08 so I was thinking it was a 427 version of the 3:08 from either '66 or '67 although it had the smallblock u-bolts and not bolted caps on the u-joints figuring that someone swapped them. With all the other projects around, this car has sat in storage since around '91. Pulled it out of storage recently to freshen up a few things and while I was under the car, I looked closer to the diff code and noticed that the code wasn't AT but was actually
ATW 032 E2. So much for it being from a 66/67. I saw that they went to Julian dating somewhere in the early '70's but realized I still needed to find the actual cast date on the drivers side of the pumpkin. Well, I found it and it reads 'A 1 8'. This diff housing is super clean with no grease or dirt to be seen since I wound up taking the whole car apart and that last character looks like an '8' and not a '3' but from the old posts I've run through, it looks like '78 diff codes started with an 'O' and not an 'A'. Anybody know what year this could be from?
Thanks,
Mike T.

 

If it's any help, "Corvette By The Numbers" says that all ’75 – ’82 diffs were stamped the same way: e.g. OH C 218 1

OH = Axle Prefix 3.55

C = Assembly Plant (Buffalo, NY). Nine different assembly plants are listed!!

218 = 218th day of the year, 06 Aug 78

1 – First Shift

The code on my '78 diff is OK 123 W8 E1. I worked that out to be:

OK = 3.08
W = Warren, Michigan
123 = 123rd day of 1978.
1 = First Shift

This left the 8 next to the W, and the E, unaccounted for. I havn't established what the 8 signifies, but I guess it could be "1978". But an ‘E’ was used to indicate Positraction up to 1974, after which Positraction was standard. It is not clear from the book whether they carried on stamping an E after ’74but since there is an E on my (and your) diff this suggests that they did.

 

Thanks for the feedback. It's looking like that '8' on my diff could just be a '3' that filled in that small area during casting. The only thing is that every time I see someone post '73 differential codes, there's no AT listed.
Mike T.