When did C2/C3 diff rear covers cast dates begin

[Wayne M.]

Was always under the impression that the 3871375 cast rear differential covers (used early '65 to 1976 ?) were un-dated prior to about 1969 model year, and that any C2's with a date must have a cover "grandfathered" from a decade later. [Date appears at the flange nearest the filler plug]

But here's what looks like an original unmolested real early 1968 unit, assembled 21st August 1967, carrier cast F-22-7 [June 22nd 1967] with a "375" cover sporting a cast date of F-7-7.

Here's the eBabe link:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=280165576420&ssPageName=STRK:MEWA:IT&ih=018

I know some on the DB must have original "unrestored" C3's, and they may wish to comment. I believe Joe L. still has his 1st owner '69.

[Joe L.]

Re: When did C2/C3 diff rear covers cast dates beg

Wayne-----

My known-original 1969 cover is dated "H 4 9" or, of course, August 4, 1969. My car was built mid-September, 1969.

[Alan Drake]

Re:C2 diff rear covers cast dates beg

Have an original 64 diff with the markings "B14" by the fill plug. It's a 303 with the GM6 on it. Owned since Aug67, second owner never replaced diff so that goes back to spring 66. Have access to original owner if needed.

Now the B14 may not be a date code, but its location seems to lead itself to a date code. Have heard no date codes existed on the 64 housing, but I do not know.

email me for pictures, akdselectman@hotmail.com
Alan

[Joe L.]

Re:C2 diff rear covers cast dates beg

Alan-----

Are there "screw heads" on either side of the "B14"?

[Wayne M.]

Two "303" covers without dates

Auto load pic is off a January '64 assembled 4.56 diff. Note fine thread and fine-thread plug on top. Dated "375" covers that I've seen have the date on the flange just below where the upper plug lies. Lower plug is coarse-thread, for comparison.

Second pic (link below) is another "303" off an early 1965 model year VIN 014xx car with 4.11 diff carrier assembled Sept 16th '64. But it has a hybrid coarse thread plug (also shown in the auto-load pic). I have never heard this configuration reported elsewhere.

[Alan Drake]

Yes on Screw Heads *NM*

[Harry Sadlock]

Re: Two "303" covers without dates

Wayne, best I can recall the 303 cover with a GM 3 cast had the fine thread and a metal vent. The 303 with the GM 4 had the course thread and a plastic vent.

Harry

[Joe L.]

Re: Yes on Screw Heads

Alan-----

Then, the marking does represent a date.

[Wayne M.]

Mine are opposite your description

Harry -- the pic link attached to my post above shows a GM_3 cast cover and has the coarse thread and the plastic vent.

Just checked the Jan '64 cover (auto-load pic of above thread) and it is GM_2 mould and has the metal vent.

But you are probably correct in relating the changeover(s) to the mould #.