Date code stamp on 65 rear end

[Ken H.]

Hey Folks,

I have a rear end that came with a 65 I bought, and the date stamp on the underside has the 2 letter gear code, then the month, day and last 2 digits of the year with some spaces beteen them. I saw another unit with the same stamping method on e-bay just a few minutes ago.

my question is that I had read on Colvin's "corvette by the numbers" that this is not how the stamp should read. Is the above description for the stamp correct, or is this rear end (and the one on e-bay) from some other source?

Also, were all of the 65 rear ends posi, or were there open units too? Colvin said there should be an indicator for Posi units, but there is nothing on the stamp I have points to it. When I bought the car, the owner said it was the original rear end, but the dates are wrong for this to be true (rear end is 8 months later than the car's build date).

Thanks in advance!

Ken

[Jack H.]

Re: Date code stamp on 65 rear end

Yep, that's the general stamping sequence for a rear end of that era.

The 2-digit alpha code denotes how the rear end was 'stuffed' (gear ratio, BB vs. SB, posi or std).

You'll find a nice picture of a typical rear end in Noland Adams '63-67 Fact Book (pp 312) as well as the broadcast code decode tables (pp 342). Additionally, your copy of the Judging Guide should provide supporting text.

Last, it's not uncommon to discover a paper 'stick on' label bearing the 2-alpha broadcast code on the opposite side of the rear axle's stamp pad.

[John H.]

Re: Date code stamp on 65 rear end

Hey Folks,

I have a rear end that came with a 65 I bought, and the date stamp on the underside has the 2 letter gear code, then the month, day and last 2 digits of the year with some spaces beteen them. I saw another unit with the same stamping method on e-bay just a few minutes ago.

my question is that I had read on Colvin's "corvette by the numbers" that this is not how the stamp should read. Is the above description for the stamp correct, or is this rear end (and the one on e-bay) from some other source?

Also, were all of the 65 rear ends posi, or were there open units too? Colvin said there should be an indicator for Posi units, but there is nothing on the stamp I have points to it. When I bought the car, the owner said it was the original rear end, but the dates are wrong for this to be true (rear end is 8 months later than the car's build date).

Thanks in advance!

Ken

Ken -

The format you describe was very common, with no separate "E" (for the Eaton posi unit); photo of my '67 3.36 Posi stamping below. The first two letters in the stamping describe both the ratio and whether or not the unit has Positraction.

There were several variations of differential housing stampings, and the Colvin book doesn't cover them.

[Gary R.]

Re: Date code stamp on 65 rear end

posi was an option and most had it but I did a 65 open diff last year as well. Unless you have history on the car who knows what you have. If both wheels rotate together it is a factory posi, this does not hold true for a tuned posi as the springs are not installed in those. Few of us still build those so chances are yours has the springs if it's a posi. The 65-68 posi's were weaker and more prone to cracking then the 69-79 posi cases,both are Eaton's just different design. If you have the diff out or plan to, it's a good idea to pull the cover,drain the oil and take a good look. If you go to carlisle next week stop by L116 or the Friday seminar I'm giving and I'll go over what to look for and how to check it.
Gary

[John L.]

Re: Date code stamp on 65 rear end

Ken:
Here's a picture of a date code for a standard '65 3:36 rear end
Nvc-001s.jpg

[Ken H.]

Re: Date code stamp on 65 rear end

Thank you all for the responses - The 2 pics that were sent are exactly what I have stamped on mine. It is an AN stamp which I believe is a 3.55 rear end per colvin's book. I am pretty sure it is a posi unit, but will need to crack it open to see for sure. I do know from the stamp that it is not original to the car - build date for the car is late Feb '65 but the rear end is dated October '65 and has the March - forward casting # on it. With that date I need to check the '66 alpha code to make sure the "AN" is still the 3.55 gearing.

I have a '58 I am finishing up and then will probably get started on the '65 early next year.

Thanks again for the help - invaluable as usual!

Ken

[Wayne M.]

Re: Date code stamp on 65 rear end

......Last, it's not uncommon to discover a paper 'stick on' label bearing the 2-alpha broadcast code on the opposite side of the rear axle's stamp pad.

Or, better still, a stamping of the 2-character code on the top flange of the carrier. Here's the 'FA' from my late 396; also shot of bottom "full stamping" from same car. Third pic is off a Feb 67 BB car. Looks like they made a grinder pass on the latter, (as surface prep for the stamp ?).

Don't know when they started this or for how long it continued.

[John C.]

Re: Date code stamp on 65 rear end

Hey John, searching information on rear ends and came across your post. I also have a 65, final assy was may 27th of 65. I'm trying to check most of the cars components to see if everything is correct and dated correctly. Would you mind taking a look at the pic of my differential and tell me what you can make of the stamp. This is a 300/327 car.
Thanks John,
JC

[Jim D.]

Re: Date code stamp on 65 rear end

John, as posted in your other thread, it's a 3.36 non-posi small block rear axle. The build date lines up perfectly with your car.
Here's a couple pics. of the rear end stamps on my April 10th built small block 65 (3.36 posi) and my May 5th built big block 65 (3.55 posi).

[John C.]

Re: Date code stamp on 65 rear end

Thanks Jim, that does help. I looked everywhere in the archives trying to find the codes that depict the gear ratio.
So it appears the rear end isn't any different from the other dated parts on the car. Technically, there isn't any real way to verify the rear end is original to the car. The rear end, just like a water pump, may or may not be original, but as long as it's dated correctly, it is acceptable and will pass judging ?
So when you see or hear someone say the rear end is "numbers matching" to the car, they are ignorant of the fact there is no such thing ??????
JC

[Leif A.]

Re: Date code stamp on 65 rear end

Thanks Jim, that does help. I looked everywhere in the archives trying to find the codes that depict the gear ratio.
So it appears the rear end isn't any different from the other dated parts on the car. Technically, there isn't any real way to verify the rear end is original to the car. The rear end, just like a water pump, may or may not be original, but as long as it's dated correctly, it is acceptable and will pass judging ?
So when you see or hear someone say the rear end is "numbers matching" to the car, they are ignorant of the fact there is no such thing ??????
JC

John,
When you read this statement, it is typically regarding exactly what it says and that is that the "numbers match" up with the build date of the car. If the statement was " born with" that would be a different matter altogether. This is without a doubt one of the more controversial areas of our hobby...the much used/abused/misunderstood term..."numbers matching".

[Michael J.]

Re: Date code stamp on 65 rear end

So it appears the rear end isn't any different from the other dated parts on the car. Technically, there isn't any real way to verify the rear end is original to the car. The rear end, just like a water pump, may or may not be original, but as long as it's dated correctly, it is acceptable and will pass judging ?

The rear end code and date is not judged in flight judging, so that doesn't matter.