When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm just a bit confused by these numbers on my diff.
perhaps you numbers guys could decipher this.
Looks like OD 21 8 W. 71
I'm a bit confused by the 71 on the end. My car was built late 76.
Closer shot of the 71.
And a close up of the OD
OD = 1976-1977 code for 3.36 ratio, 218th day of the year, Warren plant, 1977, 1st shift
The 71 isn't 1971 its 7 for 1977 (just final digit of year) and the separate 1 is for the plant shift.
This is my interpretation based on others I have decoded but I'm not familiar with any idiosyncrasy of the 1977 model year. The OD code was used for both years but it's interesting that they also used an "LR" code for 3.36 ratio for those years. Yours has an underlying "R" so maybe a restamp OD over a previous LR code? Maybe LR was more common during the 1976 production and OD for 1977? Someone else should know better than I.
OK, I understand what your saying about the numbers. But if my car was built late 76. Came off the assembly line on the first of Dec. The 218th day of the year makes perfect sense. But wouldn't the code be a 6 instead of a 7? Or did they stamp them for model year?
I've had the car for about 35 years. Never had any reason to believe its not. I bought it as a very low mileage, good used car back in the 80's. The original owner gave me receipts for everything he ever had done to the car. Including replacing the valve cover gaskets 4 times. One replacement caliper. Etc. Etc. The car was totally factory stock at that time right down to the wing nut on top of the air cleaner.
So, that's why I'm asking about numbers.
That's certainly a possibility, although I was fairly certain I have all the old service records from the original owner. Perhaps, judging by the date code. That the diff was replaced under warranty and as the owner didn't pay, didn't keep any receipts for it. Back then, the car would have had only a one year warranty. So, I know the date it left the factory, but I do not know when it left the dealership. In my former home town. Way up in Northern Wisconsin. It likely wasn't purchased or picked up until spring of 77. Giving a warranty period until spring, (approx May) of 78.
the Engine and transmission numbers match. Just this number thing with the diff. And I am no NCRS type of owner, And it probably doesn't matter much. But I am curious.
It is possible they ran out of existing year parts and started using next year parts. I once had a very early build 81 that had some 80 parts on it from the factory. This happened all the time both at SL snd BG. I would not worry about because it is probably original to the car.
There appears to be something funky about '77 Corvette differential stamps... Here are three other CF postings about '77s with date codes that don't appear to be possible for their cars:
Does any know what the gear ratio is on my 77 L82 automatic TH400 is?...
Here are the date codes on the bottom of my rear end.
AO 259 W7F1
it might not be the original rear end. Do these codes make sense?
The 259th day would be Sept. 16th, 1977, which corresponds with the 1978 model year.
I have a 1977 L48 with a manual transmission. Just curious about the rear end. The code stamped on the bottom is OA 2 33 W 7 E 1. From what I've been able to find out so far is that it's a 3.08 posi, but I'm wondering about the manufacture date. My C3's build date is September 1, 1976. Can anyone help me out with this?
I don't know if the next one is the same car as the last but the threads have different owners:
The numbers on the diff are: OA 23 3 W 7E 1
The 17S402430 is the VIN derivative
The 233rd day would be Aug. 21st, 1977, which also corresponds with the 1978 model year.
The two/three cars above have that 7 after the W but their Julian date would put the axle dates after their cars were built.
I'm thinking we're interpreting the coding system incorrectly.
Diff numbers
