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Username Post: ID & Dating a Rear Diff        (Topic#359757)
Senior Member
Posts: 913
Loc: Etobicoke, Canada
Reg: 10-25-05
02-09-20 09:49 AM - Post#2786165    

Tried finding info on dating the rear diff's that I have and not having any luck.
Any info would be greatly appreaciated.


The first diff:
This one did still have the round tag with one hole attached, and confirmed to be 3.36 gears.

From what I can see at a certain angle is a K 1 1 on the passenger side

The Second diff:
No tag

Stamped A B 1 1 2 9 on the passenger side

Found the following online, which confirms the casting number to be correct.

Casting numbers and casting codes

The casting number for a 1957-'61 non-posi center case should be 3725899

I'll be Frank, this hobby isn't getting any easier.
58 Delray in disaray


Posts: 57

Loc: Burlington, Ontario
Reg: 12-22-15
02-09-20 01:37 PM - Post#2786186    
    In response to Techhead

Frank: Check the 1961-1964 Fullsize Chev forum. There has been an interesting discussion recently on the identification markings for 1964 rear diffs. It may be helpful. John

1958 Chevrolet wagon (Yeoman)
1961 Impala convertible
1964 Impala Sport Sedan (parts car)
1958 Biscayne 4dr Sedan (parts car)

Member #51
Posts: 8900

Loc: Mustang, OK, USA
Reg: 12-25-99
02-09-20 04:03 PM - Post#2786197    
    In response to 58Yeoman

The first picture had me stumped------------------ ---UNTIL I SAW YOUR ARE IN CANADA!!!!!!!!!!!!!!!!!
The casting number, 3725899, is for a 57-later NON-posi case. Those cast in the USA (Detroit and Buffalo plants) have a casting date next to the casting number and do not have a letter inside a square. I have not seen more than a VERY SMALL amount of Canadian cases, so I cannot expand on them.
Look elsewhere on the case for a casting date.
The STAMPED K11 would be an ASSEMBLY date of Nov 11 (USA STAMPED dates DO NOT include the year, which is always in the casting date, as in the below picture).

The first picture of the second rear is from the Detroit Gear and Axle plant. The casting date K220 translates to Nov 22, 1960. In the second picture, the AB1129 translates to a 3.36, assembled on Nov 22 (remember, the year is on the other side in the CASTING date).
This is slightly unusual------------BUT NOT IMPOSSIBLE. The molten iron was poured in the mold and it was assembled on the same day!!!! It takes a while for the hot iron to cool down enough to be removed from the mold and then be cool enough to handle through the machining and assembly processes (USUALLY, casting and assembly dates are 2-3 days apart). SOOOOOOOOOOOOOO, I would speculate that it was cast on the first shift of the day, then machined/assembled during the second shift (maybe late in the second shift).

Attachment: 100_0812.JPG (1.17 MB) 4 View(s)

Senior Member
Posts: 913
Loc: Etobicoke, Canada
Reg: 10-25-05
02-09-20 08:29 PM - Post#2786212    
    In response to DZAUTO

Thank you Tom.

So the gear housing was swapped out at some point in its life.

I will also check the Canadian Diff to see if it has a stamping on the right axle housing.

Lost of info in that thread but all pertains to the 64 rear.

I'll be Frank, this hobby isn't getting any easier.
58 Delray in disaray


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