727 vs 904

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To the best of my limited knowledge, a 727 is good for around 500 hp. Meaning the major parts. But to launch that Hard, and not have issues, you need to upgrade several key items. About 900 bucks, just for the parts , and that was 6 months ago...
 
Ironracer, sounds right. Of course, A & A has these transmissions that are built to withstand much more power than 500.
 
The 383 two barrel trans only has 3 frictions in the direct clutch; just like small block 727s; that's the weak point. All other bb trans had four direct frictions except the hemi; which had five. I build 727s with six direct frictions for over 1,000 horse all the time; and 904s with five (which is what it takes to handle 500 horse); red eagles of course.
 
CudaFactHackJob said:
The 383 two barrel trans only has 3 frictions in the direct clutch; just like small block 727s; that's the weak point. All other bb trans had four direct frictions except the hemi; which had five. I build 727s with six direct frictions for over 1,000 horse all the time; and 904s with five (which is what it takes to handle 500 horse); red eagles of course.
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I fail to see how you could build a 727 to handle 1,000 horse and think that it's weakness is that it only hold 3 clutches. At much less power than that you should be using an aftermarket drum which in all probability will hold plenty of clutches. Add in the cost of that drum, and an aftermarket roller clutch, and good valve body plus labour, etc, you could easily be at or better than $2,000.00 imho.
The main weakness on some 727 is an aluminum front planetary that will strip the splines.
 
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CudaFactHackJob said:
You just love to mis-quote me don't you Duane? And that's why they changed the angle of the splines.
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Where did I miss quote you? I know about the spline angles. At 1,000 horse if it has aluminium, it will strip those splines regardless of spline angle. Not all had aluminum though, and I am just saying that if you are going to put any major power through a 727 and value your legs, you need an aftermarket drum, not a stock replacement. Good parts cost money.
 
They're not my legs. Good parts do cost money; especially for a 904; because it needs a ton more of them than a 727. Mis-quote: "it's weakness is that it only hold 3 clutches"...there, for what good it'll do..
 
CudaFactHackJob said:
They're not my legs. Good parts do cost money; especially for a 904; because it needs a ton more of them than a 727. Mis-quote: "it's weakness is that it only hold 3 clutches"...there, for what good it'll do..
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We are having communication breakdown. What I meant to say using a bad combination of words, is that if a guy wanted to build a 727 say to handle 700 horse, and he already had a 383 3 clutch 727, I would not tell him not to use it. I would explain to him that the stock drum, regardless of it factory clutch count, should not be used for the intended application. By default every aftermarket performance drum is usually manufactured for an increased clutch count. It makes no sense for them to manufacture a high dollar
Explosion proof drum for $700.00 that holds 3 clutches.
IMHO a responsible performance 727 builder should be making his customer aware of this. Not waiting till his stock 6 clutch drum blows up and he loses a leg or his car catches fire and burns to the ground. Hot trans fluid will indeed burn. I've seen it on a 12 second street car. Now having said all this and without a whole lot of trick
Potentially unnecessary parts, you could still be at $2,000.00
From that perspective, a 904 with a stock 5 clutch drum from the wreckers is much cheaper to build and safer with its factory riveted
Roller clutch and a stock drum that does not blow up. The .15 performance gain the 904 has is a bonus.
 
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Jeeze, who said not to use it? The point is; a basically stock 727 with a stock rebuild is stronger than a $1500 904. I know you guys have been pushing the 904 for years, and builders are making a ton of money off the special parts, but for 95% of the readers on here, a 727 is the only way to go. The problem is; folks are making their decision without even comparing a 727 clutch plate to a 904 plate. Just look at both rebuild kits and see the difference; that's about all it would take, but guys already have a 904, so they want to convince themselves not to cut a driveshaft and mess with different linkage. Lay a 904 friction on a 727 friction; then decide. Oh, and no more worries about cracked junk 904 converters.
 
CudaFactHackJob said:
Jeeze, who said not to use it? The point is; a basically stock 727 with a stock rebuild is stronger than a $1500 904. I know you guys have been pushing the 904 for years, and builders are making a ton of money off the special parts, but for 95% of the readers on here, a 727 is the only way to go. The problem is; folks are making their decision without even comparing a 727 clutch plate to a 904 plate. Just look at both rebuild kits and see the difference; that's about all it would take, but guys already have a 904, so they want to convince themselves not to cut a driveshaft and mess with different linkage. Lay a 904 friction on a 727 friction; then decide. Oh, and no more worries about cracked junk 904 converters.
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Not disagreeing with this post. I just think you should build the 727 according to the intended use. The engine does not have to make a lot of power to break the roller clutch. An argument could be made that a stock 904 roller clutch is better than a stock 727 as it is riveted to the case. Although I agree the 727 has more clutch surface than 904, 5 clutches at high line pressure is sufficient for most performance applications using the 904.
When you use the word weak, I think of breakage of parts.
I do not know that it is correct to say less clutches in the front drum is weak. I think it has more to do with firmness of shift or slippage.
The 727 is a great trans. It just has a few weak potentially breakage prone areas at a certain performance level that the right version of 904 will not. The 999 version will not explode a drum, the roller clutch cannot spin in the case, and the front planetaries are steel on the splines. If you addressed those areas in a 727, then it is way stronger. But like you said for most guys on here the 904 is plenty strong enough and potentially cheaper to build, mainly because you don't need an aftermarket drum.
Other than that, I agree the 727 is much stronger.
 
My old 440 race duster ran 11.001. It had a 3 clutch front drum. The guy that built it way back in the late 70s said it has less rotating mass. Kim
 
oldkimmer said:
My old 440 race duster ran 11.001. It had a 3 clutch front drum. The guy that built it way back in the late 70s said it has less rotating mass. Kim
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Yes you can sometimes get away with less clutch if you raise the line pressure. Less clutches is less weight = faster car
 
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