early 64 rear end differential date stamping question

[Brian M.]

My '64 built 3rd week of Nov 63 has a 1970 rear end in it. The rear end is shot and I can barely turn the vehicle, so I have to rebuild. I thought it might be good to get a properly dated rear end. I know the part number is supposed to be 3818753-N, and as a 3.08 it should be stamped CJ and then have the axle assembly date.

I have read several sources stating that the axle assembly date usually predates the vehicle assembly date by 1-2 months. However, if I look at the Noland Adams survey data in his book, there is a date stamp of 10 31 63 being used in vehicle 104348 (nearly 1100 before my car-probably an end of first week of November car build date), and then an axle built on 12 26 63 went into car 108477.

Given the data points above, this would suggest that for my vehicle, with a build date of 3rd week of November, I would need a 2nd week of November axle assembly date -- and that is a lot different than the guidance being provided in a few restoration guides (survey suggests it's 1-2 weeks not 1-2 months).

Is it possible that St. Louis was not consistently using their assembled axles in a FIFO or LIFO basis, causing severe sequence/date skewing, or is it my brain that is skewed? I know this request may seem overboard since these numbers aren't even judged, but I thought I have to go through all this work to drop the rear end, might as well get the right rear end back into the car.

Thanks in advance for any advice or guidance. I'm a big boy, so you can tell me if I'm crazy...it won't be the first time.

[Harry S.]

Re: early 64 rear end differential date stamping question

Correct, no FIFO, LIFO or anything else. I think the process was, what can I grab first that is on the build sheet. My April 20th 63 has an April 10th built rear.

[Wayne M.]

Re: early 64 rear end differential date stamping question

.... for my vehicle, with a build date of 3rd week of November, I would need a 2nd week of November axle assembly date -- and that is a lot different than the guidance being provided in a few restoration guides (survey suggests it's 1-2 weeks not 1-2 months).......

No need to restrict your search to a 1-2 week diff assemble window prior to car build. For instance the '65 NCRS guide doesn't mention this span, but DOES say the interval between carrier cast date and assembly has been observed to be 4 - 12 weeks.

Here's another example on a 4.56 diff, cast J-18-3 (Sept) and assembly stamped CF 1-3-64 (Jan 3rd). This same rear suspension has spindle supports dated A-6-4 (Jan 6th) and L-7-3 (Dec 7th). I don't know what the VIN of the car was, but there's probably a 4 month spread between earliest cast # and vehicle production, especially as there was little demand for the 4.56 ratio.

Then you'll need a 3830303 rear cover as well.

[Brian M.]

Re: early 64 rear end differential date stamping question

so there is a cast date and a stamped date? I saw vague reference to this in the resto guides but could not completely understand it. this diff is so rusted that I have, nothing is really readable on the exterior.

[John H.]

Re: early 64 rear end differential date stamping question

so there is a cast date and a stamped date? I saw vague reference to this in the resto guides but could not completely understand it. this diff is so rusted that I have, nothing is really readable on the exterior.

Brian -

The diff housing casting date is on the driver's side, partially hidden by the front edge of the camber strut bracket.

[Brian M.]

Re: early 64 rear end differential date stamping question

Wayne-what is the build date ofthe car with the sept cast diff and jan assy date stamp? I'm guessing mid january?

[Brian M.]

Re: early 64 rear end differential date stamping question

Hi John, thanks for your photo (I think I recognize your car from Carlisle-u pull a trailer with it?).

[Jim P.]

Re: early 64 rear end differential date stamping question

Brian,
My car was built a couple weeks before yours (103934). The build date on the trim tag is 30 Oct 63. The assembly date stamped on the differential is 10/23/63, just 1 week prior to the build date. The transmission is 10/21/63. Not sure about the cast date of the diff housing. Jim

[John H.]

Re: early 64 rear end differential date stamping question

(I think I recognize your car from Carlisle-u pull a trailer with it?).

Nope, must have been someone else's car.

[Jim D.]

Re: early 64 rear end differential date stamping question

For instance the '65 NCRS guide doesn't mention this span, but DOES say the interval between carrier cast date and assembly has been observed to be 4 - 12 weeks.

My 65 rear was cast A 15 5 and assembled 3 29 65. The engine and trans were assembled the same day.

[Brian M.]

Re: early 64 rear end differential date stamping question

thanks, that makes sense. I think my engine is nov 6 assy dated, closer i can get to that seems to make the most sense. now if I could just find one!! Checked with Bairs, Ikerd and a shop in FL. Sanity check with everyone--definitely do the later model posi hardware, right??

[Wayne M.]

Re: early 64 rear end differential date stamping question

Wayne-what is the build date ofthe car with the sept cast diff and jan assy date stamp? I'm guessing mid january?

Brian -- I think even late January would be my guess, unless it was installed shortly after the rear suspension assembly was delivered from Warren MI. The latest dated component was cast Jan 6th, and only 641 of these installed (2.9% of the entire 1964 production), so it may have sat in St.Louis for weeks before being pulled for installation. [assumption: ratios segregated by pallet -- guessing at 6 assemblies per].

Don't know the car dates / VIN as I bought it off a guy from Calif. who moved to Oregon. Was removed from car in 1968, so a low-miler.