1. TheSkunk

    TheSkunk Active Member

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    Looking to rebuild a 904 out of a doba for my Lebaron. But have some questions.

    1. Do I need to worry about tailshaft or transmission overal length?
    2. How can I determine what series of 904 it is for parts without the tag?(missing)
    3. What rebuild kit, shift kit, and upgrades do you guys recommend?
    Trans won’t see more then 450 horse 450ftlbs and 3:55 gears and street tires.

    I’ll worry about converter once I decide on my engine combo.
    Thanks in advance guys!!
     
  2. Mikes5thAve

    Mikes5thAve Well-Known Member

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    1. Tail shaft from one car to the other is the same. But the transmission needs to come from the same engine family. No using big block transmission on small block for example.
    2. Look for the part number on the transmission housing on the lip over the pan.
    3. Get the most durable parts that you can and hope for the best. Like I said in the previous engine post for durability you're better off using a 727 over a 904 if you're making any kind of power in a street application.
     
  3. Camtron

    Camtron Well-Known Member

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    I’ve been kicking around ordering a trans rebuild kit and valve body from Cope Racing. I haven’t any experience with the products first hand, but I’m at a similar cross road of figuring out what to do with my transmission. Far as I know all their parts are made in the US and assembled by John Cope himself. They do everything from stock rebuild kits to complete high performance race transmissions and everything in between.
    Here’s a link to their rebuild kit that I’ve been eyeballing:

    https://www.coperacingtrans.com/?product=904-rebuild-kit-street-high-performance-72-up
     
  4. TheSkunk

    TheSkunk Active Member

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    Awesone and mikes5thave I appreciate the concerns about the 904 vs 727 but I’m gonna try and use what I have before my old man kills me for dragging more parts home lol.

    And Camtron I’ll look into them

    thanks guys keep them coming guys.
     
  5. Mikes5thAve

    Mikes5thAve Well-Known Member

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    John Cope is a good guy to deal with.

    Can't blame you there. That's why I've used 904s in the past too.
     
  6. Davesmopar

    Davesmopar Well-Known Member

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    I would only use a transgo sift kit..... Gil Young pretty much pioneered the shit kits....

    One thing he does is corrects the factory screw ups when reprogramming the valve body....

    I am using a TF3 shift kit and absolutely love it. The car lunges forward even at lower RPMS when sifting into 2....
    But the rear spragg is a week link in the transmission if taking off in drive... always best to pull down into low 1st.... that applies the low/reverse band which supports the spragg and keeps the transmission happier....

    I converted the valve body to a full manual.....

    Just my humble opinion......

    I do plan on building a spare 904 cause I know I will kill this one at some point..... lol

    Edit: with said kit you can check fluid levels in park, no more neutral....

    Also put a A500 pan on it, much deeper with drain plug... $30.00 or less
     
  7. TheSkunk

    TheSkunk Active Member

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    So would you rebuild with one of the cope kits and then suggest running a trans go shift kit? Upgrade the rear sprag for insurance? And this should live behind a mild small block on the street?
     
  8. Duke5A

    Duke5A Well-Known Member

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    If you're going to use Cope parts, call the guy and ask. He builds 904s for use behind big blocks in balls out race applications. He'll set you on the right path.
     
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  9. Oldiron440

    Oldiron440 Well-Known Member

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    I know of a couple of E/SA cars that run 10.s with 727 that have 904 internals because of the lighter weight of the components.
     
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  10. Davesmopar

    Davesmopar Well-Known Member

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    Doing a quick check I see he uses transgo sift kit TF2 in the 904-3 pro street auto trans..... he aslo uses the 4.2:1 band level which I also use, stock in mine was 3.8.... its all about timing the shifts. If they overlap it will bind for a split second making you think it barked the tires but really locked up....

    Anyway here is the link.....

    https://www.coperacingtrans.com/?product=904-3-pro-street-automatic-shift


    But it never hurts to call the company either for advice..... 20191101_15452018.jpg 20191029_182028390.jpg 20191029_205435569.jpg 20190212_115819.jpg 20191209_144443291.jpg
     
  11. BudW

    BudW Moderator Staff Member

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    During the time frame of FMJ's, they made 3 different styles of the A904 for two different engine classes.
    No A904's (from factory) were ever made to fit behind a big block.

    The A904 engine groups are for /6 and for the small block.

    I use the term “A904" – just because I've used it most of my life, but the different versions of that transmission family are:
    A904 (-'83?) - Light Duty
    A998 ('79-83?) - Medium Duty
    A999 ('76-'89+) - Heavy Duty (HP, Police or Towing)
    Of those three, there is the lockup and non-lockup (converter) versions.
    Note: I have conflicting data about when the A904 and A998 were no longer available for M-bodies.

    Most of the A998 and A999 (but not all) have the more desirable low gear ratio in it (which is what many racers use or will modify to make fit into the above mentioned big block).

    Lockup transmissions came out mid-year 1978 – but, was an option to “order” non-lockup for many years afterwards. The key word is car was “ordered” that way.
    All of the cars on dealer lots all came with lockup transmissions after a build date of early 1978.

    The wide ratio gear set (the desirable one) came out in 1980 and was fully integrated into the A904 family by 1981 – so all '81 and newer A904 appearing transmissions have the good gear set in them. None of the '79 or older transmissions have it. Some of the '80s have it - but not all.

    The best way to tell – as well as to make sure of any other replacement parts is to get the numbers which are stamped on the oil pan rail on drivers side (under the shifter levers) which is called the TIN (Transmission ID number) – which ties into your question # 2
    iu118LRCP5.jpg
    iuT3F0LX1D.jpg

    The last 8 or 9 digits of the VIN are stamped onto a pad on other side of transmission – which doesn't help us in this aspect.

    The A904-A999 can be a good transmission choice. It is smaller, lighter and can handle a lot of HP in a modified form.
    The A904/A998 – not as much HP in stock form

    All A904/A998/A999 all were the same length and all used the small slip yoke (aka 904 slip yoke – 26 spline / 1¼” inner diameter)

    All (car) A727's were the same length - but longer than the A904 family (roughly 4.1" longer). Note: they also have a 4*4 version and a HD truck short shaft A727 – but neither are suited for car usage (no slip yoke).
    The A727 slip yoke is 1-7/16” inner diameter / 30 spline.

    I'm going to intentionally not answer your question #3.
    BudW
     
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  12. TheSkunk

    TheSkunk Active Member

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    Thanks guys I’ll be sure to pick Mr cope’s mind. I’ll have to get out to the garage and look for the number on my spare trans I have. I also have 3 other slant six 904s that I could rob of internals correct? I’m under the impression that it’s the bell/case and inputs that are different between the sb and slant trans?
    Bud you seem to know your stuff so maybe you can answer that question? And do you mind explaining your reasoning for not answering my 3rd question earlier? Just curious if it’s due to everyone having a different preference or..?

    thanks guys
     
  13. BudW

    BudW Moderator Staff Member

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    The case is the biggest difference, but there are a few other differences, but minor.

    A person can remove the guts from a SB A904 and insert into a /6 A904 (again, A904 is used as a generic term) and vice versa - in most cases without issue.

    Another difference is most /6 (except for HD, Taxi or Police service) usually use fewer clutch disks per clutch assembly – which means can handle less torque overall. The more clutch disks per clutch pack = more torque capacity – which isn't a concern for most /6 or 318 2-bbl engines.

    Another difference is planetary carrier pinions. Most /6's and 318's use 3-pinion planets
    A904 3-Pinion Rear Planet.jpg

    Most 360's (or bigger) use 4-pinion planets. There is not really any difference other than more moving parts – other than more pinions can carry more torque.
    A904 4-Pinion Rear Planet.JPG

    The planets used for Diesels have 6-pinions (but for a A727 or A518).
    A727 6-Pinion Rear Planet.jpg
    If you noticed the planets are made out of either steel or aluminum. I don't know the material makes them any stronger or not – but the aluminum are lighter and just feel better to me.
    If I needed a planet and had a good steel and aluminum ones in front of me, I would grab the aluminum one, providing the pinion count was the same (or higher). I have had thousands of Chrysler planetary's in my hands before.

    Most /6 and 318 2-bbls have different governor spring/weight setups (ie: shift points) - than performance engines (or police engines). Sense I'm a Chrysler trained transmission tech, I prefer to use factory parts for performance engines (engines that make more power at higher RPM's – over using aftermarket shift kits – but that is my opinion (only). I have many friends who has used the popular shift kits with good results.

    Lastly – there are numerous changes of minor parts over the years. Most of which would not stop a person from changing all of the guts, or major subsections from one year to another or one engine size to another – but sometimes it can.
    Like in the case of the rear planets, there was a spline count change made in the mid '80's (I think), so a person has to use the output shaft with rear planet – if a difference in year of parts was being considered.


    Most /6 transmissions (A904 or A727), except for HD or police units, had the least desirable parts inside – BUT that doesn't make them not handy for parts. Items like front pumps, Input and output shafts, and many other parts are exactly the same (within the two different transmission sizes) – except for the minor between-year differences
    BudW
     
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  14. TheSkunk

    TheSkunk Active Member

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    Thanks again bud! Any chance I could bug you one more time lol? My spare trans i finally got the numbers off the side of it-

    4028464 5526 0214

    is this trans gonna give me any surprises when I go to order rebuild parts or anything I need to look out for sense your the man it seems when it come to Chrysler trans!!
     
  15. BudW

    BudW Moderator Staff Member

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    There should be a "PK" stamped first, which means built from Kokomo assembly plant.

    "4028464" - '76-77 passenger car 318 2-bbl A904 standard-duty non-lockup.
    Note: this should be the very same transmission I have in my '77 wagon.

    "5526" is the 10,000 date code that Chrysler uses.
    In this case, that transmission was built on Wednesday, September 13, 1976

    "0214"
    214th unit built that day.


    Unrelated to you, the front pump gasket and/or front pump bolt seals are leaking on my wagon – so I need to take my transmission out to reseal it. I have an '84 police A999 in my garage that I've been considering rebuilding instead and installing into my wagon. The '84 has the preferred low gear set – which will result in better takeoffs (than your '76 A904), it will have higher shift points than existing A904 and is a lockup – which will give me about 5-10% better fuel mileage than I currently get.

    If I was building an A904 series transmission – I would definitely strive for the '80 and up low-gear set.
    The lockup/non-lockup could be debated, but if you plan on driving the car much, I recommend you go with lockup for the better fuel mileage.
    BudW
     
  16. Mopars1

    Mopars1 Member

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    The three best 904 family transmissions to start with are these part numbers. 3681844, 4028465, 4028878. These are all non lockup and have the five clutch front drum as long as someone hasn't changed the parts with another trans.
     
  17. Remow2112

    Remow2112 Active Member

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    No lockups! But they are great for stealing the lower first gear. Alto red clutches, Kolene steels, and kevlar bands. Trans go shift kits are the only way to go unless you got to Cheetah and buy their valve body. If you want to retain auto shifting put use the TF-2 kit. Don't waste time with TF-1.

    If you do go with a TF-3 (full manual) make sure you pin the kickdown back in the case vs externally. Had a guy pin it back externally with a ziptie (Stupid) and the ziptie broke.

    904 can be built to handle up to 550 hp but most of them get torn down about once a year to check for wear.

    Dan...
    PS. Cope is a good dude.
     
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  18. SRTMirada

    SRTMirada Well-Known Member

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    My preference is to start out with a 1981 or later 999 lockup transmission. Then get an early 1970's 904. I take the converter, pump and valve body from the 904 and put it in the 999. There is a small amount of lathe work to accomplish this. The result is a transmission with no lockup and lower ratios. Part numbers are listed above but I've never seen one. What I'm suggesting is easy and cheap and provides the best drivability and fun. ( except fuel economy )
     
  19. MiradaCMX80

    MiradaCMX80 Well-Known Member

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    Interesting read here. Last night I learned my 80 Mirada is a lock up 904. I've been a Mopar fan my whole life and didn't know Chrysler used mechanical lock up transmissions in the late 70's/early 80's.

    I've posted asking for advice on how to warm up the little 318 and a member suggested gears and a higher stall TC before a 4 barrel. So this raises questions.

    I believe my axle is a 2.9 ratio 8 1/4. I'd like to freshen it and install 3.23 gears. How will this affect the lockup on my stock trans? Are there higher stall TC's for lockup 904's? Or, should I look for a non-lockup 904/999 and build to suit, using a better selection of non-lockup converters? Fuel mileage from a lockup is not a concern...but the shuddering I have read about would be.
     
  20. BudW

    BudW Moderator Staff Member

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    After mid-year 1978, the only way to NOT get lockup was to special order the car (or cars with towing package). I'm not sure what the percentage of special order cars were total – but would guess (maybe) 10% - and of those, how many would select non-lockup? I know people avoided them when a transmission replacement was due – but I think they got a bad rap. I prefer lockup's now because they get roughly 10% better fuel mileage. That is a huge plus for me.

    The torque converters look the same from the outside. The factory put a paper stickers on them when built – but for most of us, who expects a paper sticker to stay in place 40some years later?
    Note: Pickups with trailer towing packages, or ¾/one ton trucks usually didn't get lockup until the CAFE fuel ratings got so high, they couldn't avoid it.

    The input shaft spline count are different between lockup and non-lockup. A904/A998/A999 (and the 4-speed variants) non-lockup input shafts (1968 and newer) will have 27 splines. Lockups have 26 splines and about 1/2” (13 mm) of no splines at front of the shaft.
    A727 (and its 4-speed variants) non-lockups have 24 spline input shafts and lockups have 23 splines (and about 1/2” (13 mm) of no splines at front of the shaft).
    Here is a picture (transmission assembled, and really dirty) and clean picture (of shaft itself) to show differences:
    727 Input Shaft Diff a.jpg
    727 Input Shaft Diff b.jpg
    the shaft with longer splines are non-lockup.
    Because of the input shaft spline difference – the torque converters are also very different inside and will not interchange.

    The front pumps and valve body are different. I'm also thinking the case is also different – but can't remember exactly.

    The A727 lockup shares the same front pump as its 4-speed cousins, as well as the A904 series lockup with its 4-speed cousins with one interchangeable difference. In the early '90's they changed the torque converter hub from a slot to a flat.
    TC slot vs flat hub.png
    This is a good thing sense the slots are known to crack over time causing problems. What this means is ANY A727 (or its 4-speed cousins) lockups or ANY A904 series (or its cousins) with lockup will interchange as long as you replace the front pump gear set to correspond with the torque converter hub design (hint, go with the flat design). That said the two above mentioned groups will not interchange with each other (the A727 has a bigger hub/pump gearset than the A904 series).
    A727 A518 flat pump gear.jpg

    If I was building (or getting rebuilt) a transmission and you wanted a specific stall converter – call a torque converter specialty shop (like TCI or others like them) and give them your car weight, engine size, HP, gear ratio (and maybe other details) and they will make a converter just for you. It won't be cheap but it will last forever and it will do what you want it to.
    BudW