Rear End Numbers

[`Michael Southard]

These differential numbers don't seem to work for 66' or 67' in the Noland Adams book.

The stamp code on the bottom is "ATM 1 3 67". It doesn't look like any thing in the book. The "AM" part of the code could be the 3.36 Posi, But why is there a "T" in there? That "T" is kinda mis-stamped too, it's a little higher and toward the "M". I guess the 1 3 67 could be "Jan 3 1967"???

The casting number stamped on the rear "3830303" of the diff seems to work for any mid-year.

There are additional numbers: Passenger side "3899143-N", Driver side "J-76".

It also appears as though the engine HEAD casting numbers "8782461" were used in many applications? But what is the number to the right of the casting number, "1144"?

I do believe I did verify that the body (VIN 30837S116445), does go with the frame (#S116445). So I guess the body, frame, and trany are all 63'. I was hoping at least the heads were.

Any thoughts are appreciated.
Mike S.

[Kevin Whiteley]

Re: Rear End Numbers

Mike,

3899143: 67-69 (model year) Corvette differential. "J76" is October 7, 1966, which is the day the diff. was cast. This fits with the diff. stamp date "1 3 67", which is the date the entire differential was assembled (Jan. 3, 67). Still don't know what the "N" means.

3782461: which you identified as 8782461. These were used on 64 only Passenger, Corvette, and Chevelle 327's. For Corvette, they were used on the 300hp, 365hp, and 375hp options. Given that you have a 63, I don't think these are the original heads. Check the valve sizes to accurately determine the application. If 2.02/1.60, they would have been for the 365hp or 375hp option. "1114" indicates January 11, 1964 cast date.

I couldn't find a reference for "ATM", but "AM" is a posi 3.36:1 ratio, while "AT" is for 427 posi 3.08:1 ratios. If the "T" is a "1", then that could be a mis-stamped (misplaced) shift code, which normally preceded the two-digit axle code. I think there should also be another letter after the date code. If you can take a picture, that might be helpful.

Got this info from the same source as before. Hope this helps.

Kevin.

[`Michael Southard]

Re: Rear End Numbers

That was Al Colvin's, Corvette by the Numbers? I'll be at the book store tomorrow.

[Tracy C.]

why not just order online from the NCRS bookstore? *NM*

[`Michael Southard]

Re: why not just order online from the NCRS bookst

I have ordered a couple resources from them, Not aware they had that particular book. I'll look a little closer.

[John H.]

Re: why not just order online from the NCRS bookst

The "N" after the casting number on the diff indicates that it's nodular iron as opposed to grey iron.

[`Michael Southard]

Re: why not just order online from the NCRS bookst

"Grey" cast iron is the same used in engine blocks... (very machinable)correct? What exactly is nodular then?