1967 differential identification

[Al M.]

I'm trying to verify my differential is correct for my car. I'm finding some conflicting information and want to be sure it's correct. The car is a 427 with auto trans. build date is early january 1967. The tank sticker shows option No. 02G81JA and is defined as 3:08 ratio positraction. The casting number on the differential housing is 3899143-N. The new 67 vette judging manual does not indicate an N after the casting number. The casting date is H226 which seems reasonable for a January car. The casting number for the cover is 3871376 but the new judging manual indicates it should be 3871375. There is also a K36 cast in the cover. The assembly code indicates AT 11 30 66 which should be good as well. But when looking at pg 208 of the manual, it does not show an AT as being available with a powerglide. Only a 4 speed. Can anyone verify for me whether what I have is correct?

[Joe L.]

Re: 1967 differential identification

I'm trying to verify my differential is correct for my car. I'm finding some conflicting information and want to be sure it's correct. The car is a 427 with auto trans. build date is early january 1967. The tank sticker shows option No. 02G81JA and is defined as 3:08 ratio positraction. The casting number on the differential housing is 3899143-N. The new 67 vette judging manual does not indicate an N after the casting number. The casting date is H226 which seems reasonable for a January car. The casting number for the cover is 3871376 but the new judging manual indicates it should be 3871375. There is also a K36 cast in the cover. The assembly code indicates AT 11 30 66 which should be good as well. But when looking at pg 208 of the manual, it does not show an AT as being available with a powerglide. Only a 4 speed. Can anyone verify for me whether what I have is correct?

Al------


Everything lines up just fine. The "N" is seen after the casting number on most, if not all, of these differential cases. It represents "nodular iron", the material the case is cast of.

You are reading the cover casting number incorrectly, which is common with casting numbers. There was no cover of casting number 3871376 so yours has to be 3871375. For casting numbers, "6" and "5" are often confused.

The AT-coded differential was definitely used with 427 with Powerglide. "AT" represents 3.08:1 with positraction as you've noted and that ratio was optionally available for 1967 427 with Powerglide.

[Wayne M.]

Re: 1967 differential identification

...... There is also a K36 cast in the cover. The assembly code indicates AT 11 30 66 which should be good as well. ...... Can anyone verify for me whether what I have is correct?

Al -- is the K36 cast inside (on the concave surface, oil side ? Or is it on the flange that bolts to the carrier, near the fill plug ? If the latter, you probably have a 1976-era cover, as I believe covers didn't have the castings dated until calendar 1969, or thereabouts. Pic below is of a January 9th, 1969.