727 or 904?
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!!
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.
