DD is 3.31 gears for 66-69. 09 27 is September 27, K is McKinnon Industries.
Casting # on Center Section will be 3852980, the casting date will tell the story.
Casting date looks to be on the bottom of the center housing, facing forward.
So far I'd say it looks like it might be the corrrect one for your car. But, the bracket for the brake hose is missing.
If you've got the Protect-O-Plate, the engine, transmission & differential #'s will be on it.
It looks like a posi unit with an aftermarket ring gear spacer behind it. That posi will have originally been used on a 2.73, 2.56 or 2.29 gear set. It will be fine for the street but on a 2 ton car with sticky tires on a racetrack guys shear those longer ring gear bolts off that are required when you use that spacer.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
On the 70 diff I have in the alley the casting date appears to be on the very bottom of the casting, facing forward. The passenger side facing forward didn't have anything.
It's on saw horses, and has the pinion facing the wall. I crawled under for a look, but had some lights shining in my eyes so I couldn't make out the casting date.
-- Edited by seventy2plus2 on Monday 5th of February 2024 07:36:43 PM
In the wide shot you provided showing the internals of the diff (and the posi carrier), on the left of the posi carrier will also be its casting number:
ED 32088 2 series 2.73:1 & down,
30140PM1 3 series 3.07:1 - 3.73:1,
EDB 30174 4 series 3:90:1 & up.
As Carl says, spacers can be used to put the wrong gear set on another carrier.
The 3 series carriers are the ones that are worth money. I think I have both empty 2 series & 4 series posi carriers in the garage.
Strictly a guess but I'm thinking it's a set of thick 4.10's made to fit a 3 series carrier. Then, because he didn't have a 3 series carrier he got a 2 series carrier and use a spacer to make it equivalent to a 3 series carrier. Make sense?
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
If it does turn out to be a 2 series carrier you can just keep the posi unit you have and use the 3.31's with the spacer. It will be fine for what you are going to use it for.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
If you have a 3 series posi, then rebuilding it would be the way to go. If you have to go and buy one, then rebuild it, then I'd just spent the extra and get a new Eaton 3 series posi.
In the wide shot you provided showing the internals of the diff (and the posi carrier), on the left of the posi carrier will also be its casting number: ED 32088 2 series 2.73:1 & down, 30140PM1 3 series 3.07:1 - 3.73:1, EDB 30174 4 series 3:90:1 & up. As Carl says, spacers can be used to put the wrong gear set on another carrier. The 3 series carriers are the ones that are worth money. I think I have both empty 2 series & 4 series posi carriers in the garage.
Here's the date code casting from the diff in my garage. I think it shows F 16 9, which would be July 16 1969, sounds good for a 1970 Impala. This date code is on the very bottom of the case facing forward.
