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First timer 904 rebuild/upgrade help
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Author:  Reed [ Tue Feb 02, 2010 11:18 am ]
Post subject:  First timer 904 rebuild/upgrade help
Hello all. This weekend I will be attempting my first ever transmission rebuild. I want to take a slant six 904 and build it up to be as strong and durable as possible for use in a van that regularly hauls heavy loads.

My plan at the moment is to take the 1973 slant six 904 that I have in the garage and upgrade it with all the guts out of a v-8 904. My understanding is that this will give me larger and more clutches and drums (don't know what the drums in a tranny are yet, I'll find out on Saturday), and a better planetary gearset.

My questions:

What years v-8 guts will bolt into a 1973 slant 904 housing?

I would love to upgrade to a wide ratio gearset. Can that be done without swapping to a lockup torque converter or do I need the lockup stuff too?

Will v-8 lockup hardware bolt into a 1973 slant 904?

Can I even use the wide ratio gearset out of a mid 80s v-8 transmission in an early 70s slant 904?

Alternatively, if I am able to locate a wide ratio slant six transmission, can I upgrade the internals of that using v-8 guts?

If these are simplistic questions that have been answered before, I apologize and beg your patience and indulgence. I know so little about transmissions at this point that I don't even know what search terms to use to find this info.

Thanks in advance.
Author:  volaredon [ Tue Feb 02, 2010 12:36 pm ]
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not that hard a job; got a Service manual, even an old Chilton's, with what used to be called the "unit repair section" would be great, or an older "motor's"; alot of the older ones would walk you thru pretty well. be careful on the piston seals that you don't pinch them or fold them over themself. Do the air checks before putting the valve body in. this is a "verification" that everything to that point is OK, better to find out now than once installed and full of fluid. a rubber tipped blow gun and ~30PSI is all you need;
you dont need to worry if you can't regul;ate your line down that far; in that case just "crack" the valve on the blowgun; don't "give 'er Hell"
while doing this you'll see the servo or band acuate as you apply the air to the passage. and as far as the clutches, you should be able to hear them apply or at least feel them do so putting your fingers on the outside of the drum as you apply the air. each passage will only work 1 function.

Good old Vaseline works fine as assembly lube; and also soak your clutch discs in a bowl of ATF as you go.

What you (should) gain with the V8 guts will be deeper drums that hold more clutches; meaning it will hold more power. and yes you can use the low 1st gear planetary w/o the lockup. they are seperate functions. the input shaft and valve body are different between L/U and non L/U versions.
Among even the same-year 904's depending on orig application, they vary quite a bit as far as number of clutch discs in each clutch pack. you'll see this as it comes apart what I mean.
Author:  Reed [ Tue Feb 02, 2010 12:57 pm ]
Post subject: 
Thanks! So I guess I will use the non-lockup 73 slant 904 case and partial guts, but get the complete guts out of a wide ratio V-8 tranny. I will keep the non-lockup parts and just swap in the better gears and the better clutch packs and drums.

Thanks a million!
Author:  Fopar [ Tue Feb 02, 2010 1:26 pm ]
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Just a tip on installing the lip seals. Get some mylar sheet and cut a piece big enough to almost wrap completely around the seal, use Vasoline to lube and stick the drum with the mylar wrapped around it into the hole. Just push down and it works like a ring compressor. Once the piston is seated pull the mylar sheet out. :shock:
Author:  Reed [ Tue Feb 02, 2010 1:45 pm ]
Post subject: 
Mylar, isn't that what the shiny balloons sold at grocery stores are made of?
Author:  Fopar [ Tue Feb 02, 2010 1:50 pm ]
Post subject: 
It is also the same kind of stuff page protecters are made of. :lol:
Author:  mpgFanatic [ Thu Feb 04, 2010 11:15 am ]
Post subject:  Re: First timer 904 rebuild/upgrade help
Quote:
I know so little about transmissions at this point that I don't even know what search terms to use to find this info.
Not to be a smart ass, but if you go to Google and enter Torqueflite, you'll find a wealth of knowledge... ;) But I know this only because I was recently curious for this type of info, myself.

My favorite pages are at allpar.com, where a number of folks have collaborated to describe the Legendary Torqueflite. Then, at the bottom of their summary page, there's a reference to more detailed information written by Tom Hand. His work is lengthy and priceless. By the time you've read all that, your fears should be alleviated quite a lot.

A search for "torquflite 904 rebuild" will turn up several different magazine articles with step-by-step photos. I recall that one of them showed a special tool used to compress a clutch pack into a drum-- reminded me of a piston ring compressor. But other than that, it looks fairly straightforward.

If you can't find a tranny with the wide ratios, it's apparently possible to purchase a brand new planetary gear set, in several flavors of strength (factory heli-cut vs. race straight-cut, and various ways of welding the center hub.) A Google search for "Torqueflight 904 low gear set" will point out some possibilities.

- Erik
Author:  SlantSixDan [ Thu Feb 04, 2010 11:50 am ]
Post subject: 
Be sure to use the governor assembly that goes with the planetary set you're using. They're different for the wide-ratio gears; if you mismatch, it'll be impossible to set up the shift points correctly.

There's a Torqueflite manual here.
Author:  Reed [ Thu Feb 04, 2010 12:01 pm ]
Post subject: 
Thanks guys. I have been googling 904 rebuild quite a bit lately. There are some good article with pictures on mopar magazine pages, and the pages on Allpar are great. I have also been searching this site looking at previous questions about rebuilds. Plus, and this is the greatest, Josh Skinner was kind enough to let me call him and pick his brain about his recent experience rebuilding the 904 for his Valiant.

The conclusion I have come up with is that I will use the case from a 1973 slant six 904 but I will swap the complete guts of a mid 80s V-8 904T, 998, or 999, depending on what I can find in the junkyard. I won't mix and match parts; I will just remove the guts from the v-8 case, clean, replace worn parts, install the shift kit, and bolt it all into the slant six case. The slant six guts will go into a plastic tub and be set aside for future use.

I have a 1984 Dodge van FSM to guide me, and I will be purchasing/renting the necessary tools to do the job right. I have already downloaded the ATSG manual Midi so kindly posted, and I have been reading it and the FSM.

I am keeping my fingers crossed that at this time next week I will have a clean and rebuilt heavy duty slant six 904 waiting to be installed in my brother's van.
Author:  SlantSixDan [ Thu Feb 04, 2010 12:25 pm ]
Post subject: 
Quote:
I will swap the complete guts of a mid 80s V-8 904T, 998, or 999, depending on what I can find in the junkyard. I won't mix and match parts
I'm not 100% sure that is possible; it seems to me there's something with one of the bands that is not compatible, so you may need to re-use some of the original 904 components.
Author:  Reed [ Thu Feb 04, 2010 12:27 pm ]
Post subject: 
I believe later transmissions had a wider low/reverse band (and I could be completely wrong on this), but I am hoping that by keeping all matched components together I won't run into any problems.
Author:  SlantSixDan [ Thu Feb 04, 2010 1:14 pm ]
Post subject: 
Keep us up to date!
Author:  Reed [ Thu Feb 04, 2010 1:25 pm ]
Post subject: 
If you really want me to, I will take a bunch of pictures and do a minim tech article waling through disassembly, cleaning, parts swapping, and reassembly. I know I can tend to "share" too much, so I will try and keep the commentary limited and focus on the pictures, if people are interested.
Author:  adiffrentcity [ Thu Feb 04, 2010 5:56 pm ]
Post subject: 
Pictures are good! So is commentary! Look forward to seeing your walk-through.
Author:  Reed [ Thu Feb 04, 2010 7:10 pm ]
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I'l do my best to take notes and good pictures. Unfortunately, once I get into a project, I often forget to come up for air and take pictures.
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