727 vs. 904???

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68dart-sb

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I have a 68 Dart, /6 with a 904 transmission. Removing that for a 318, wanted to go with a 360, but the 318 will have to do.

The 318 will have a purple shaft cam, (nothing way out there, but it will not be stock) The 318 will have a four barrel.

The rear is currently 7.25, but will be going to 8.25 with a posi-trac rear with 3.55 gears and street tires. Dart will be used for street driving and one or two times a year down the strip for fun!

(I know the 904 that is behind the /6 will not work, this is a different transmission.) (Do not think it matters, but it will have a set of 74 Dart front disc brakes and I plan on lowering the car 1" all the way around.)

The question is, I have both a 727 and 904 small block transmissions, both are in good shape, which one to use, and why????


Thanks in advance for your thoughts.

Sam
 
Use the one that is cheapest to get installed and running...

which is probably the 904 since you could use the /6 converter plus the driveshaft is the correct length..

remember...904 converter does in interchange with a 727 ...also the 727 is about 3.5 to 4 inches longer then the 904..there for the drive shalf would need to be shorten..
 
904. It's smaller, lighter and takes less power to turn. Plus like stated your drive shaft will work with it.
 
Plus you can put a lower first gear in it and give it a more push at start.
 
I had a similar question. My '69 dart has a "built" 904 (shift kit installed by prev. owner). I am putting in a 340 engine, shooting for about 400 HP. will the 904 withstand?

I also want to change gears in the 8 3/4 from 3:23 to 3:55 or even 3:73's
 
904 will be fine as long as it was built properly. Don't really need anthing exotic in it, just quality parts and put together properly.
 
I have a 904 with a shift kit in mine, first with a 273 that was 11:1 and the 904 handled it easily. Now it is attached to a 340, bored .030 and it runs smooth.
 
I'd use a 904 too. Easier to install since the car already has a 904 and it consumes less power. Should even get a little better fuel mileage since it consumes less power to operate it.
 
The best 904 to use is the one's that came in 72 & later. Their bigger and can stand more HP.
 
The 904 came out of a 72 Dart - the 727 came out of a late 70's - early 80's truck. Both attached to 318s. Both have been checked over and are in working order.

Everyone likes the 904, any concerns about the strenght of the 904 compared to the 727?

Please tell me a little more about the 904 consuming less power "it consumes less power"? I am leaning toward the 904, but still have some concerns?

Which converter to use? I have the /6 converter, the 904 converter and the 727 converter?

Which converter to use?? Why??

Thanks, Sam
 
Converters won't interchange. They are 904 or 727 specific.

Make sure the 727 trans isn't a lock-up converter type. A lock-up trans would have the splines machined at the tip that goes into the converter.

Chrysler did a lot of testing in the mid-'70's. They found that, built equally and with the same spec converter, a 904 was about .15 faster in the 1/4 mile than a 727. The reason being is that it has smaller, lighter components and a little less friction internally. But it may not be obvious with your set-up.

If getting it rebuilt, find someone familiar with performance applications, particularly Mopars. Not just any trans shop.

When I got my first car a looooong time ago, I went through 3 727's in a year with a basically stock 340. But I was abusing the heck out of it because I didn't know any better. Just a shift kit helped transmission life after that because there was less slippage and heat.

I have a 904 built by JW Transmissions in Rockledge, FL in my race car. Nothing trick, just a good, solid performance build. I believe the "red" clutches and/or bands are the better ones. I run easy mid-11's in the 1/4 with the wheels in the air every run, footbraking. Last trans was in for 4+ years and I had it redone just to be on the safe side. You shouldn't have any problems with a properly built and maintained trans in your application. An auxilary trans cooler and synthetic fluid always provides extra insurance. Synthetics reduce wear and hold up better against heat - the #1 cause of trans failures.
 
Locomotion said:
The reason being is that it has smaller, lighter components and a little less friction internally.
Click to expand...

Just to clarify, this is why the 904 "consumes less power" or, there's less engine horsepower loss through a properly built 904 because of the smaller, lighter components and less internal friction.
I'd suggest making your choice based on your intended use. Primarily race, then go with a built 904 to maximize power to the pavement. But if almost always a street car, I might think more about the 727 since they're basically 'bullet-proof' if built correctly.
Consider all the options and then choose wisely.
 
Heck with that. Even on the street go 904. Like stated run an aux cooler too. My 904 has been in my car since 05 or 06, tons of street miles and quite a few low 12 second quarter mile trips. Shifts as good today as it did the day I put it in.
 
I agree with above comments on using the 904, the 727 use to be the way to go but it's been proven the 904 is more than sufficient and takes less power from the engine. If you were running a heavier B-body or a truck then I'd go with the 727 but the extra strength isn't needed with an A-body.

The 727 is worth more so sell it and spend the cash elsewhere.
 
Blownfish said:
If you were running a heavier B-body or a truck then I'd go with the 727 but the extra strength isn't needed with an A-body.
Click to expand...

Thanks for reminding me. As another plug for the 904, I forgot to mention that my race weight is 3,540+ lbs!
 
My 904 seems to go out too often. My car weight is 3,700 before the stereo, amps and subs went it, lol. With a 340 and open windows on the freeway I need a powerful system if I wanna hear the tunes. Its built with red clutches, ect. Its back at the shop right now! The trans guy brother was like 5 years ago telling me the 727 is much stronger and easier to adjust the shifts for the right firmness for street use...but I needed that 25 more hp:pale:

Oh, the shop isn't ripping me off, stuff is sometimes repaired free or cheap.
 
sounds like you need a new shop. may be cheap and not ripping you off but they also sound liek they don't know what they are doing.
 
dodge freak said:
My 904 seems to go out too often. My car weight is 3,700 before the stereo, amps and subs went it, lol. With a 340 and open windows on the freeway I need a powerful system if I wanna hear the tunes. Its built with red clutches, ect. Its back at the shop right now! The trans guy brother was like 5 years ago telling me the 727 is much stronger and easier to adjust the shifts for the right firmness for street use...but I needed that 25 more hp:pale:

Oh, the shop isn't ripping me off, stuff is sometimes repaired free or cheap.
Click to expand...

3700 pounds? what kind of car? That is getting up there for a 904 if you have any power, especially if you ad a couple hundred pounds of stereo, a passenger and your self to that 3700.

The way you drive also has a lot to do with the longevity of the tranny.
 
79 Magnum---I live by muti lane roads and freeways. I don't know, hope it be alright. I did just get a 10 inch streetfighter converter so maybe now the trans can shift harder without breaking the tires loose at light throttle.

A 904 can hold power but needs fast shifts. On the street with certain converters you could be barking the tires on each shift even 1/4 throttle and be having a few motorists calling 911 on 1/2 to full throttle up shifts as you go fishtailing 1st to 2nd gear. With race converters not nearly as much. You can tame it down of course but then it wears out quicker. The 727 trans has more grip and can last longer with mellow shifts, the dude who retired there was telling me.

Oh well, at least its at a cool place. Been going there for like ever, lol
 
If you plan on running headers ,the 904 will give you alittle more room to work.Both the 904 and 727 are great trans.I've run them both.Lighter car 904,heavy,727..
 
I like the 727 myself. It is heavy duty. Probably not needed but that is my only reason. Nothing wrong with a "right" 904 as the racers will tell you.
 
904 sure has a better rep than when I had one . I blew 4 of them , shift kits and coolers on them and they still went . Then I put a 727 and for 7 years no problems .Of couse this was in the late 70's and late 80's , they must have improved them going by all the recommendations here
 
I don't know. Or people are babying their old rides now since they are worth more than when they were 10 years old, ha ha.

My 904 had the front clutch go out at 1,600 miles on a hd rebuilt. Now place was super cool and did all the work for free--even r/r the trans. Guy was pretty sure it last this time.

I will see--will say it seems great so far.
 
Thet were sure with me as well , until the 4th trans blew , then got the lawyers letter saying my face was no longer welcome .
Hope that things have improved and you never have problems .
 
I gotta admit in the old days (70's and 80's) we would never think of using a 904 in a performance application cause it seemed they didn't even hold up well to a stock 318. But we were kids then and ran the snot out of everything, never changed the fluids regularly, and never let things warm up good, and who ever needed a trans. cooler anyway... LOL Today's transmission fluids have improved and so have friction materials. Even what is considered stock friction material today is better than it was 30 yrs. ago. Another thing is several shift kits sold back then weren't really very good. To us kids we thought if the trans. snapped your neck when it shifted it was great. Now we know that sometimes that neck snapping ability some shift kits produce actually aren't good because it is possibly overlapping gears while shifting.
 
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