Differential Stamping Location on Top of Housing Too?

[Thomas H.]

Rebuilding the differential from my 67. Took the housing to the shop to be degreased and once all of the crud was off I noticed an "AZ" stamped in the top of the housing as well as the normal area on the bottom flange. The font used is the same as the one on the bottom. Was this a normal occurrence? I don't recall seeing it stamped on the top on my 66 or 71 cars.

Tom IMG_3590.jpg IMG_3589.jpg

[Bob J.]

Not a stamped code but many 63s I've owned had the last letter of the code written in yellow paint on the $_57 1963 4.11 rear end case.jpg top of the rear.
Bob Jorjorian

[Thomas H.]

I just went through the pictures of when I did the diff in my 66. Ya know, you take tons of pictures and never seem to have the one you need........ But I was able to find one where a single "L" is stamped in the top of the housing ("AL" being the stamping on the bottom).

[Gary R.]

I have seen some stamping on the top but not a lot. Sometimes it is just one letter but most of the 100's I rebuilt did not have top stamping.

[Edward C.]

They might have run out of the paper labels that you sometimes find on that area.
I don’t have access to my pics right now but I have pictures of the paper label, very similar to the two letter valve cover labels you see on the valve covers, that they would place on top of the diff. My pics are from a 69 but they might have done that for earlier cars as well. Many of those labels didn’t survive so I’m not surprised many people might not know they were there.

[Joseph S.]

Not a stamped code but many 63s I've owned had the last letter of the code written in yellow paint on the $_57 1963 4.11 rear end case.jpg top of the rear.
Bob Jorjorian

Bob, Great example. This is pretty common in 1963!

One thing I'm noticing on that rear end, like most that I have seen, is NO blackout. There is no evidence that the center section was ever painted.

[Mark F.]

...Many of those labels didn’t survive so I’m not surprised many people might not know they were there.

My guess is these markings, whether painted; paper-labelled; or stamped were put there when the diff was assembled in Warren MI to help ensure the right ratio got assembled into the rear suspension module subassembly at St. Louis, which took place in the basement. Particularly with the paper versions, my guess is they were not meant to last very long - just long enough to make it thru Warren assembly; then the 8-hr. trip from MI to MO + some storage time there. As we see in the photos, the painted and stamped versions obviously lasted much longer.

Per John Hinckley's C2 Assembly Process Presentation (available in the Database of Restoration Documents [DoRD] Sticky Post), here's what he says about the frame upside down (FUD) line at St. Louis:
...Install rear suspension module (subassembly up from basement elevator) which included the suspension crossmember and cushions, differential and nose bracket, half-shafts, trailing arm assemblies, strut bracket and rods, and rear spring with the ends free). Bolt crossmember and differential nose bracket to frame, install rear jounce bumpers and big-block rear stabilizer bar...

[Tony S.]

On the top of my 1965 differential case is the capital letter "N" stamped on the top. That coincides with the gear ratio for my car. Hope that helps. Tony