Hey, first-time poster here!  Thanks for having me!  Just bought a ‘69 L46 project car, and yes, I’m a Corvette “newby”, so please excuse all the dumb questions coming from me in the near future!  Anyway, my new project has the original engine and M20 trans, which is awesome!  But this rear end is baffling me!  Unfortunately, It looks to have been re-stamped.  But if you zoom in on the pic closely, you can make out an “F” under the “A”, and I’m pretty sure I can see an “A” under the “M”?  So if it was originally an “FA” rear end (HD 3.70 posi), why in the world, would someone re-stamp it to be a “CAM” rear end (non-HD 3.36 posi).  I was told that the CAM format was actually used in 1970.  But my car is an extremely late build, Q08 on the trim tag (Dec 08, 1969), so supposedly having the CAM format on there is fairly probable.  But, if my build date on the car is Dec 8th, why would the rear end be re-stamped with a “12 11” date, 3 days after the build date!?!?!  There’s just a whole lot here that doesn’t make any sense!  Anyone have any insight on this?

Mine bottling that someone would obviously over stamp something like that.  Makes no sense.

Also, you say your car was built Dec 8, 1969.  Wouldn't that be the 1970 model year?

Actually, no, the 1969 Production Year went from like Aug or Sept '68 thru the end of Dec '69.  I believe this was due to a labor strike going on at GM that year.  That's also why you hear the term "70-1/2 Camaro", the 1970 production year was delayed on some vehicles because they couldn't get the production line spooled up for a few months behind schedule.  

👍

The upside down pic makes my hed hert....🤕 😆

Kinda hard to make out anything on it, and my monitor is too large to turn upside down, but...I'll give an opinion, based on my knowledge. Yes, it appears to be a restamp on the diff. It's entirely possible that the diff had a problem once whatever car it was in was assembled/tested, and it was changed. Now...when there was an issue like that on the line, the offending part/assembly would be removed, and replaced with a different one. Any part removed would be sent to heavy repair, and they would correct whatever the issue was, and then that part would go back into circulation on the line. For the purpose of this discussion, we'll say it was a diff. The diff was repaired, and maybe the ratio changed in the process because they needed more of that ratio at the time. The diff would be restamped, and returned to the line...and possibly installed on your car as it made it's way down the assembly line. It's well documented that this type of thing happened, so it's not out of the realm of possibility. It's also possible the diff was changed/repaired at the dealer before delivery. Being a '69, and knowing some of the crap that took place during the extended year model, I wouldn't think twice about what was stamped on the diff. Of course, the only way to know for sure what ratio it has, you would need to disassemble it and see. If it has the yokes that use bolts and straps, it is a HD diff. If it uses u-bolts and nuts, it is a normal diff. Of course, the yokes can be changed, so.....we're right back where we started. If you are not having the car judged, then the diff stamp is irrelevant other than curiosity. Run it! 😉

(I had to flip it...it wuz drivin me nutz....🤣)

Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thanks for the response Adam's Apple!  I know some "sketchy" stuff happened on the production line during the extended '69 Production Year.  As you said, maybe they ran out of the AM 3.36 Posi rear ends and had extra FA rear ends already built, and had to have it re-worked for this car.  But the 12 11 date still doesn't make sense, being that it is 3 days after the production date of the car.  I guess we'll never know...  And yes, someday I'll have to take the rear end out and actually verify what's in there!  FYI, it does have the "U-bolts", so as far as I can tell, it's not an HD rear end.  Not looking to have the car judged by NCRS or anything, at least not anytime soon, so I'll have to live with it.  Besides, finding a replacement rear end that's date coded perfectly, would be like finding a needle in a haystack! 

And I was able to go back and fix the original picture....so it should be rotated correctly now!  Thanks for your help!

The VIN tag, and the trim tag(with the body build date info) were installed after paint, but before final assembly, which would mate the body to the chassis. The car could set on the assy line for several days for any number of reasons, before being actually completed. This can, and has explained many date code discrepancies. My '74, for example, sat on the assy line for 2 months waiting to be completed, due to a labor strike. I have one t-top headliner dated 3 weeks after the body build date, my smog pump is dated a few days later than the body build date, and a couple of other small items that are dated after the body build date. Again, if an item failed final inspection after leaving the actual assy line, it would go back for repairs, and could have parts replaced with "incorrect" dated parts. Always hard to prove, but the general Corvette folks know it happpens.

Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

If you want to verify what is in it, just jack it up, put jack stands under the trailing arms and let it back down so the half shafts are more level.  Then just rotate one wheel hub one turn and count the number of rotations of the drive shaft.

3 and half turns is a 3:55, 3 1/3 turns is a 3:36, and just slightly over 3 turns is a 3:08.