Where do I get info on 8 3/4 Rear DATE CODES?

[69ISFINALLYMINE]

I would like to know how to decipher date codes on 8 3/4 3rd members.  Specifically 1969 castings.

Thanks.

[EffinDuff]

They have a lot of information here.

http://www.mymopar.com/Mopar8_75RearEndGuide.htm

[EffinDuff]

From what i understand what you really want to pay attention to is the ham (center section).  it will have casting numbers on it that end in 741, 742, 489.  That will tell you what pinion style you have and you can also tell if you are running posi and what style by pulling that and looking at it. 

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8-3/4" Axle Center Section Types

The 8-3/4" axle was available in three basic types. The types are differentiated by the pinion stem diameter....1-3/8", 1-3/4", 1-7/8". The choice of axle pinion assembly was determined based on the application.

1-3/8" small stem pinion (aka. '741')>
Carrier casting numbers: 1820657 (1957-1964), 2070741 (1964-1972). This assembly was typically used in low weight/low horsepower applications through low weight/medium horsepower and high weight/low horsepower applications. Pinion depth and bearing preload is set with shims. Differential bearing setting (ie. backlash ) is set with threaded adjusters.

1-3/4" large stem pinion (aka. '742')
Carrier casting numbers: 1634985 (1957-1964), 2070742 (~1961-1969). This assembly was replaced by a phase-in of the 1-7/8" pinion starting in the 1969 model year. 1970 RW (Plymouth and Dodge mid-size) were the last models to use the 1-3/4" which appeared in a 2881489 case. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. Pinion depth and bearing preload is set with shims. Differential bearing setting (ie. backlash ) is set with threaded adjusters.

1-7/8" tapered stem pinion (aka. '489')
Carrier casting numbers: 2881488, 2881489 (1969-1974). This assembly was introduced in 1969 and was phased-in to replace the 1-3/4" unit through 1970. Note: the 1-3/4" pinion also appeared in some '489' carriers during this period. By 1973, the '489' was the only unit available in passenger car applications. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. Pinion depth is set with shims, preload is set with a crush sleeve. Differential bearing setting (ie. backlash ) is set with threaded adjusters.

[EffinDuff]

Some more information with pictures 

http://www.68cuda.com/rear.html

[69ISFINALLYMINE]

From what i understand what you really want to pay attention to is the ham (center section).  it will have casting numbers on it that end in 741, 742, 489.  That will tell you what pinion style you have and you can also tell if you are running posi and what style by pulling that and looking at it. 
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From what you are saying I don't see how the casting number will tell me if it is a sure grip or not, but I do know that the casting number will tell me what TYPE of 3rd member I have (741, 742, or 489).  What I am trying to find out is how to decipher the DATE CODE next to the casting number.  I want to verify the casting date vs the build date of the car.  Any help here with casting dates (date codes)?

Thanks,
Doc

[EffinDuff]

I'm not too sure.  What are the numbers you have in the Date code?  I will look around in my references to see if i can find anything.  I didnt think you can tell if it was  a suregrip without pulling the center section and actually looking at it.

[EffinDuff]

You can also tell if its a posi rear by jacking up the rear and spinning one tire.  If the other tire spins the opposite direction it is an open rear.  This wont tell you which posi is installed because i think in 69 they had both the borg and the dana power lok.


As far as verifying the date i have no idea.  Ive searched around for a while with no luck.  Sorry 

[resq302]

from what I have seen, the date coding was stamped in either yellow ink or white ink on to the one flange of the third member.

[69ISFINALLYMINE]

The date code was cast into the 3rd member next to the part number (see pic in this thread):  http://www.dodgecharger.com/forum/index.php/topic,48714.0.html
The part number cast into the housing (-741, -742, -489) will get you close to knowing the year and I do know that a '69 could have had a -742 or a -489 3rd member, but the actual date code is what I am interested in.

I want to see if anyone can provide information on how to decode those date codes.  Not guess at one particular number that I might have, but to explain how to decode any 3rd member date code for a particular model year (I am most concerned with '69).  It would be nice if they were 6902 for Feb of '69, but I know that is not the case. 

Also, not to get off-topic but I have read reference material that states that for 1970 there was usually some orange paint on the oil fill plug to denote sure grip without having to open up the rear or jack up the car and spin the tires by hand, etc.

If anyone can help on the date code deciphering let me know. 
Thanks.
Doc

[resq302]

ok, you were talking about the casting date code.  I was talking about the assembly date code.  The assembly date code was stamped on.

[69ISFINALLYMINE]

Aaaah.  Now that is very interesting.  Stamped in paint I think you said, so that would make it easily lost during a rebuild or after years of rust I would think. Yeah, for what I am trying to do I need to decipher casting date codes.  Thanks though.

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ok, you were talking about the casting date code.  I was talking about the assembly date code.  The assembly date code was stamped on.

[resq302]

I will see if I can get a picture of my diff on the car for ya.  I replicated the original markings.

[69ISFINALLYMINE]

That all sounds interesting and thanks.  Just to reiterate though, I am looking for information on how to decode casting date codes on 1969 3rd members, as most who are selling the 3rd members only have casting dates available for selection.  Thanks again.

I will see if I can get a picture of my diff on the car for ya.  I replicated the original markings.

[resq302]

The date code that is in that pic on the other link that seems to be cast into the housing appears to be a Julian date code.  Bascially if you do a google search, a Julian date code goes by the actual day of the year.  1-365.  Again, if you do a google search, they have it already broken down so you just have to find the Julian number and then find out when it corelates to what month and day of that year.

[69ISFINALLYMINE]

Thanks for the information and thanks for sticking with me, resq302.  That helps a lot.  I will look around for information on that topic and if I find anything usable I will post it here.  I do find it surprising though that someone hasn't broken this information down into some sort of a topic or chart by now on this site for various years.  It seems like it could be pretty handy to a lot of people who are going for originality or stock and need that info.  Anyway, THANK YOU again and like I said, I will post what I find.

Doc
('69 Charger, H-code 383, 727, other options.....)
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The date code that is in that pic on the other link that seems to be cast into the housing appears to be a Julian date code.  Bascially if you do a google search, a Julian date code goes by the actual day of the year.  1-365.  Again, if you do a google search, they have it already broken down so you just have to find the Julian number and then find out when it corelates to what month and day of that year.

[John_Kunkel]

The link below has some date coding info:

http://www.mmcdetroit.com/Understanding_Date_Codes/

Although third member castings aren't specifically mentioned the link suggests that some heavy castings use the 10,000 day calendar coding method. I have a 489 housing with a 3033 date code which would be November 16, 1969 on the 10K calendar and consistant with the '70 model year; BUT the date stamped in the ring rear is 12-5-73 which suggests the date code on the casting might be March 3, 1973.

[Just 6T9 CHGR]

My 489 case has "1699" on it.....

If it was the 10,000 day calendar it would translate to a 2/21/1966 date.....which is too early for a 489 case...
Courtesy of LightningJar.com
http://www.lightningjar.com/decoders/10k_day_calendar/

I think using the day of year method would be more accurate....169th day of 1969 (June 18th, 1969)

John, the 303rd day of 1973 was 10/30 so it could jive with your ring gear date

[BROCK]

THE FORMAT is dddy. SO 0470 WAS MADE ON THE 47th DAY OF 1970, FEB 16. 
FOR LEAP YEARS JUST ADD 1 TO EVERY NUMBER PAST 59.


Jan.....Feb.....Mar.....Apr.....May.....Jun.....Jul.....Aug.....Sep.....Oct.....Nov.....Dec
.01......32.......60.......91.....121.....152....182....213.....244....274.....305.....335
.02......33.......61.......92.....122.....153....183....214.....245....275.....306.....336
.03......34.......62.......93.....123.....154....184....215.....246....276.....307.....337
.04......35.......63.......94.....124.....155....185....216.....247....277.....308.....338
.05......36.......64.......95.....125.....156....186....217.....248....278.... 309.....339
.06......37.......65.......96.....126.....157....187....218.....249....279.....310.....340
.07......38.......66.......97.....127.....158....188....219.....250....280.....311.....341
.08......39.......67.......98.....128.....159....189....220.....251....281.....312.....342
.09......40.......68.......99.....129.....160....190....221.....252....282.....313.....343
.10......41.......69......100....130.....161....191....222.....253....283.....314.....344
.11......42.......70......101....131.....162....192....223.....254....284.....315.....345
.12......43.......71......102....132.....163....193....224.....255....285.....316.....346
.13......44.......72......103....133.....164....194....225.....256....286.....317.....347
.14......45.......73......104....134.....165....195....226.....257....287.....318.....348
.15......46.......74......105....135.....166....196....227.....258....288.....319.....349
.16......47.......75......106....136.....167....197....228.....259....289.....320.....350
.17......48.......76......107....137.....168....198....229.....260....290.....321.....351
.18......49.......77......108....138.....169....199....230.....261....291.....322.....352
.19......50.......78......109....139.....170....200....231.....262....292.....323.....353
.20......51.......79......110....140.....171....201....232.....263....293.....324.....354
.21......52.......80......111....141.....172....202....233.....264....294.....325.....355
.22......53.......81......112....142.....173....203....234.....265....295.....326.....356
.23......54.......82......113....143.....174....204....235.....266....296.....327.....357
.24......55.......83......114....144.....175....205....236.....267....297.....328.....358
.25......56.......84......115....145.....176....206....237.....268....298.....329.....359
.26......57.......85......116....146.....177....207....238.....269....299.....330.....360
.27......58.......86......117....147.....178....208....239.....270....300.....331.....361
.28......59.......87......118....148.....179....209....240.....271....301.....332.....362
.29................88.......119....149.....180....210....241.....272....302.....333.....363
.30................89.......120....150.....181....211....242.....273....303.....334.....364
.31................90................151...............212....243..............304...............365

[69CoronetRT]

My 489 case has "1699" on it.....

If it was the 10,000 day calendar it would translate to a 2/21/1966 date.....which is too early for a 489 case...
Courtesy of LightningJar.com
http://www.lightningjar.com/decoders/10k_day_calendar/

I think using the day of year method would be more accurate....169th day of 1969 (June 18th, 1969)

John, the 303rd day of 1973 was 10/30 so it could jive with your ring gear date

Chris is correct. The case housing casting date is 'day of year' and 'year'.

In John's case 3033 = October 30, 1973.