Need help with 12 bolt rear

[81malibu355]

Hey guys. I need some help indentifying my 12 bolt rear. I know thcasting number I found on the webbing apparently is from a 69 Chevelle. But I can't determine whether it's a 3 or 4 series carrier. Any help would be great!!

I only found 2 numbers.

The casting number I found was 3959038
The other number I found was- M1 D N

I will try to upload pictures but it won't let me from my phone

Edit. Here are the pics

 

[prairiehotrodder]

Did it come with gears? If so what ratio are they?
brian

 

[81malibu355]

The gears in it are Richmond 3.73s. I got the car with the rear already in it

 

[prairiehotrodder]

I would say then that its a 4 series carrier unless it has the special richmond "thick gears" which you should be able to identify by the part number on them.
brian

 

[81malibu355]

Thanks for your help man!

 

[SSedan64]

Car 12-Bolt 3-Series carrier allows 3.08 - 3.73 ratio stock gears, + 3.90, 4.10, 4.56 & 4.88 Aftermarket.
Car """""""""" 4-Series """""""" """""""" 4.10 & up stock ratio, + 3.73 Aftermarket.

Truck 12-Bolt 3-Series carrier allows 2.76 - 3.42 ratio stock gears, + 3.73, 4.10 & 4.56 Aftermarket.
""""""" """""""""" 4-Series """"""""" """""""" 3.73 & Up.

 

[81malibu355]

So what does that mean?

 

[SSedan64]

The Housing numbers you listed wont tell you if it's a 3 or 4-Series carrier.
3.73 gears are available for 3 & 4 Series carriers.
You'll have to look a the Stamped part #'s on the Ring gear or Casting #'s on the Carrier.
Eaton Posi's 12-Bolt Carrier casting #'s:
2-Seires = ED32088
3-Series = 30140PM1
4-Series = EDB30174

There're Stamped #'s on the passenger side Axle tube that indicate stock/oem axle ratio. Pic below.

1969 Chevelle Rear Axle Codes

Decoding Chevrolet VIN, trim tags, cowl tags, engine, engine block casting numbers, cylinder head casting numbers, intake manifold casting numbers, transmission, interior codes, and paint codes.

chevellestuff.net

 

[81malibu355]

Ok. Thank you for the help!