727 or 904?

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moper said:
If you have the 727, it will be a little heavier, it will take a little bit of power, but a basically stock one with a shift kit will live forever behind your stroker in an Abody with street sized/type tires. A 727 will live taking 500hp like it deals with 230.
A 904 will be lighter, will take less power to run, and will require more (a lot more by my definition) money to build to a level I would be comfortable with recommending to a customer. I'd get rid of the single wound spring and upgrade the drum as one mod. I'd upgrade the pump support. I run the Red Alto frictions in the ones I build. A deep pan too.
So as far as what I'd recommend - the 727 will run about $600 in hard parts to live forever assuming the driveshaft and rear stay intact. The 904 will run about $1300 in hard parts to be at a level I'd say "go for it" confidently. Both will work fine. Plenty of 904 guys get beat by 727s. If one thinks the transmission is what's making a car fast at the slower-than-10.50s range it's a mistaken fantasy. I'd build the 727. It's cheapest, because I'm broke and because most of my customers are very concerned with budgets.
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What is the reason you would upgrade the pump support and what drum upgrade are you referring to. Big piston design? Billet or what?
How about posting a $1300.00 list of parts. I am curious.
My car dropped in et from the 11.70-80 range to consistent 11.20s by changing from a 2:45 first gear stock 727 to a rollerized 2:74 first gear aluminum front drum 904 with no change to the motor. This was on a low torque 344 non ported w2 head motor.
How much is a low gear set for a 727?
The 904 in the right combination is absolutely faster potentially for much less money than a 727.
 
RockinRobin said:
It seems like the people on here that only race once in a while are more concerned with being a little bit faster.
That and the folks with unlimited budgets or sponsors (must be nice).
The poor folks like me just want a consistent car, doesn't have to be faster than so and so's car.
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Once you master how to rebuild these transmissions yourself it does not cost that much for the occasional rebuild. Like Tony has said many parts are a one time purchase investment.
It is the big dollar rebuilders who cost the occasional racer big money.
 
Wow... people are passionate about this topic!
From what I can see, both perspectives have their merits. I'm only likely to race a couple times but the reason I'm building a performance car is cuz I want it quick! Quicker than my bros bowtie cars especially! lol I will drive it hard but I won't be running it on the edge all the time. If it costs a few bucks more to speed it up a little (but still be reliable)... I'm doing the 904.
Cost isn't an issue here. I'm not rich but I get parts pretty cheap and the labor (and some training) will only cost me lots of cold beer but not much else. Friends helping friends make the world go around!
904; I think the list of 'parts' is fairly clear but I'm not sure about the valve body differences that have been mentioned. I don't mind the manual shift but do I need it for my application?
Since he's the one who has to build it. I'm going to take this thread with me to my trans guy for his opinion too.
Awesome discussion, thank you again everyone!

... and holy **** those exploding drums!!
 
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Yeah make sure your trans guy sees me say this that if he charges you over a six pack of beer to rebuild a 904 he's taking you for a ride! And if he can't do it with a blindfold on then I don't even think he's qualified. I mean don't get me wrong I have a real dislike for automatic transmissions all together. But that's not stopping me from grabbing a free 904 that was on Craigslist this last weekend. it's only $104 rebuild kit from being like new again.
 
Magster65 said:
Wow... people are passionate about this topic!
From what I can see, both perspectives have their merits. I'm only likely to race a couple times but the reason I'm building a performance car is cuz I want it quick! Quicker than my bros bowtie cars especially! lol I will drive it hard but I won't be running it on the edge all the time. If it costs a few bucks more to speed it up a little (but still be reliable)... I'm doing the 904.
Cost isn't an issue here. I'm not rich but I get parts pretty cheap and the labor (and some training) will only cost me lots of cold beer but not much else. Friends helping friends make the world go around!
904; I think the list of 'parts' is fairly clear but I'm not sure about the valve body differences that have been mentioned. I don't mind the manual shift but do I need it for my application?
Since he's the one who has to build it. I'm going to take this thread with me to my trans guy for his opinion too.
Awesome discussion, thank you again everyone!

... and holy **** those exploding drums!!
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some other things to think about.
Any 727 whether race at the strip or just performance on the street really should have a aftermarket sprague and an aftermarket drum of some kind for safety sake. Those trans can explode very violently as has been said.
The 904 has a better stock sprague and a stock drum that is not prone to exploding. Because of this the low budget approach would be that in a 904 build you do not need a drum which is true.
But a lightweight aluminum version accelerates faster at the strip at the expense of more maintenance fluid changes.
The 727 is going to be more durable because it is thicker and beefier as has been said and has more clutch surface.
But is also what makes it heavier and in a performance application makes it slower. The 904 in most applications strikes the right balance between performance, safety, and reasonable durability.
If your car needs the low first gear, the 904 has them available for cheap. So to build a safe 727 with low gear you would need to purchase an aftermarket drum, sprague and aftermarket low gear set
At major expense to get a slower trans then a junkyard 904.
Most aftermarket valve bodies run the line pressure slightly higher than a 727 to help with the lesser clutch surface in the 904(add more clutches) to help clutch pack clamp.
 
The multi spring kit is more about RPM than HP. Unless you plan to spin the engine 6K plus, not likely with a stroker, get the lower dollar reverse wound spring from ATI. That'll save you $100

Plenty of real world examples of 904's living behind 500hp strokers for a long time. It's not the 70's anymore and people have learned how to make them live with additional clutches in a 4 clutch drums, stronger band pieces, etc.

Just about any decent valve body from ATI, T/A, transact and some others will work. A low band apply is really not a big requirement in a 904 becasue that's a crutch for blowing a sprag and trying to saving the front drum. Not an issue with a 904. People say the 904 will explode.... absolutely they will. BUT, you better be able to spin the engine ~9500+, because that's what it roughly takes for the stock 904 front drum to hit critical mass. I've NEVER seen a 904 explode like a 727 will... only takes about 5000-5500 RPM for a 727 to go BOOM! That's not hard to hit even for a stock BB or SB mopar. We had a 727 explode in a station wagon that was used to tow a boat! Oh the Fun with that.
 
Well either way and or - meaning all three, all Mopar Transmissions are very good and they're extremely easy to rebuild. I tried or I should say I did rebuild a Chevy turbo 350 and it was literally two to four times as much stuff to get to the same place. Now I'm not saying one better than the other or one's lighter than the other or one can take more horsepower than the other cuz I have no idea. I'm just saying there was a lot of crap to do in that turbo 350. I almost had to think about it. So all in all Lucky us!? Anyway we go if we put our money into it it's likely going to be good for quite some time either 904 or 727 or an A833. have a good day :elmer:Subject dead....
 
crackedback said:
The multi spring kit is more about RPM than HP. Unless you plan to spin the engine 6K plus, not likely with a stroker, get the lower dollar reverse wound spring from ATI. That'll save you $100

Plenty of real world examples of 904's living behind 500hp strokers for a long time. It's not the 70's anymore and people have learned how to make them live with additional clutches in a 4 clutch drums, stronger band pieces, etc.

Just about any decent valve body from ATI, T/A, transact and some others will work. A low band apply is really not a big requirement in a 904 becasue that's a crutch for blowing a sprag and trying to saving the front drum. Not an issue with a 904. People say the 904 will explode.... absolutely they will. BUT, you better be able to spin the engine ~9500+, because that's what it roughly takes for the stock 904 front drum to hit critical mass. I've NEVER seen a 904 explode like a 727 will... only takes about 5000-5500 RPM for a 727 to go BOOM! That's not hard to hit even for a stock BB or SB mopar. We had a 727 explode in a station wagon that was used to tow a boat! Oh the Fun with that.
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An 8,000 rpm rev in a 904 with low gear gets the drum to 21,920 rpm which is kinda close. 8,000rpm multiplied by 2.74
Worst 727 drum explosion I,ve seen was not only the hole in the floor but the driver trying to get out of the car on one foot after the tranny oil ignited and the whole car went up in flames. He made it out ok with a injured foot. The car was toast.
John Cope explained somewhere on the forum that all trans brake valve bodies regardless of brand, apply the low band when the brake button is on. All of them.
The low band apply feature when discussed is pertaining to how long the band stays on after the button is released or whether it stays on until you pull second gear. The low band is applied to help the sprague withstand the torque of the motor on launch.
I paid extra to get "low band apply" on my recent purchase of a tranzact pro nitro brake even though Joe did not think I needed it because I feel it is more reliable to keep it on until the shift.
That is also how John Copes new brakes work as well. The trans would have engine braking all the time in 1st gear. My brake came with the line pressure set to 170 psi for a 904 setting according to tranzact.

image.jpeg
 
Look how simple ^^^^^^????
The pan bolts, the ten bolts on the valve body (as seen^^^), the 6 tail housing bolts (and snap ring), and the 6 bolts on the front and WALLA....
now replace all seals, clutches, and a couple bushings.....yawn... and put it back together.
I think the most influential and inspiring thing I was told about these transmissions (by one of my favorite fabo members) is "if one of my guys couldn't rebuild at least 3 904s in an 8 hour shift he'd probably be needing to look for somewhere ells to work" -
People you need to STOP with this automatic transmission boogie man stuff. It's amazing how many people would not hesitate to do a cam swap, but never think to rebuild there 904 witch once out would be easier.
 
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Did you rebuild it? Did you watch it rebuilt? Or are you like the 99% who just know what the transmission guy told you?

stroked340 said:
Did you build my transmission??..if not which you DIDN'T you haven't a clue what was done to it..:rolleyes::rolleyes::rolleyes:
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j par said:
Did you rebuild it? Did you watch it rebuilt? Or are you like the 99% who just know what the transmission guy told you?
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No I didn't rebuild it I had a highly qualified transmission tech build it with the high quality parts I supplied,he's been building transmission probably longer then you've been alive..
 
Well if he's been building 904s for over 50 years he must be a very nice Simple Man because these are very easy. I don't care how highly highly highly highly qualified overqualified someone is to change a tire, really there's only so many things to look at here.
I should have wrote it down on a piece of paper before I even said what I did. Okay first thing he's going to say is I had someone that was highly qualified. Then the next thing he's going to say is that he gave them all the great parts. And then some magic happen behind closed doors and all the sudden I have a bad *** tranny. = I don't have a clue exept what the tranny guy told me.
I mean even my myself feel that your guys probably greatly qualified and I have no reason nor you to believe that he wouldn't put the parts that you bought in there for sure. But 310% you only know if you do it yourself. Which you did not.
And just for the record to make this 100% said I am not turning this into your tranny guys qualifications I guarantee he is much more qualified than I am before I was ever born. But remember that rebuilding 904 Transmissions in particular that's not saying a lot.
And another two hours has just went by and another 904 is been rebuilt in some tranny guys shop and ready for install again.
LAST WORD...

stroked340 said:
No I didn't rebuild it I had a highly qualified transmission tech build it with the high quality parts I supplied,he's been building transmission probably longer then you've been alive..
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j par said:
Well if he's been building 904s for over 50 years he must be a very nice Simple Man because these are very easy. I don't care how highly highly highly highly qualified overqualified someone is to change a tire, really there's only so many things to look at here.
I should have wrote it down on a piece of paper before I even said what I did. Okay first thing he's going to say is I had someone that was highly qualified. Then the next thing he's going to say is that he gave them all the great parts. And then some magic happen behind closed doors and all the sudden I have a bad *** tranny. = I don't have a clue exept what the tranny guy told me.
I mean even my myself feel that your guys probably greatly qualified and I have no reason nor you to believe that he wouldn't put the parts that you bought in there for sure. But 310% you only know if you do it yourself. Which you did not.
And just for the record to make this 100% said I am not turning this into your tranny guys qualifications I guarantee he is much more qualified than I am before I was ever born. But remember that rebuilding 904 Transmissions in particular that's not saying a lot.
And another two hours has just went by and another 904 is been rebuilt in some tranny guys shop and ready for install again.
LAST WORD...
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BLAH BLAH BLAH...Simple man huh,he's probably forgotten more about building transmissions then you'll ever know..people like you make me laugh:rofl::rofl::rofl:..
 
Okay men I realize I'm rolling with the turd here and can only get one result! LOL but there's seriously needs to be some comprehension reading here I thought I made it as clear as I could that I was not trying to speak badly whatsoever about a transmission man.?
Just like most and like 340strokes-(LOL) only knows what the transmission man told him.
One more time your transmission man is a genius and surely knows more in his pinky then I will ever know in my entire life about everything and Transmissions and still the fact remains you only know what he told you about your transmission. :popcorn:


stroked340 said:
BLAH BLAH BLAH...Simple man huh,he's probably forgotten more about building transmissions then you'll ever know..people like you make me laugh:rofl::rofl::rofl:..
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Magster65 said:
The info I'm after is what mods need to be done to reliably hold a 904 together with probably double the power they were designed for.
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Well since these were designed to live behind the mighty SL6, I think you will find it difficult to actually "break" one.
Maybe it will get a little tired, but give up and die, not a chance.

My 904 is from hughes, and I have never even considered cracking one open until reading this thread.
My new garage has a nice big gas heater, and a couple hundred bucks for a good manual, rebuild kit, and an old tired core is cheap for the experience and a little holiday season entertainment...
 
stroked340 said:
No I didn't rebuild it I had a highly qualified transmission tech build it with the high quality parts I supplied,he's been building transmission probably longer then you've been alive..
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Thank You, I didn't realize I was considered a tech in your world. Having rebuilt or part of rebuilding many different autos and manuals over the years, just because we had to. Sweet ! I will call all my old friends and tell them we have been upgraded to tech status, as we have rebuilt a few 904's.
 
j par said:
Okay men I realize I'm rolling with the turd here and can only get one result! LOL but there's seriously needs to be some comprehension reading here I thought I made it as clear as I could that I was not trying to speak badly whatsoever about a transmission man.?
Just like most and like 340strokes-(LOL) only knows what the transmission man told him.
One more time your transmission man is a genius and surely knows more in his pinky then I will ever know in my entire life about everything and Transmissions and still the fact remains you only know what he told you about your transmission. :popcorn:
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Get a life will ya:icon_fU::icon_fU::icon_fU:..
 
340strokes - Quit being a poor loser and just admit the only thing you know is what the tranny man told you that is the only thing you can guarantee LOL
Actually when I stop to think about it fishmens67 probably does know more about your tranny than you do LOL
excuse the pun but "fish on" LOL

stroked340 said:
Get a life will ya:icon_fU::icon_fU::icon_fU:..
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