With your permission, I'm going to jump in here and post some information that may be controversial, but is not MY opinion; it's the opinion of someone who has forgotten more about Torqueflites that I'd learn in 10 lifetimes.
His name is Len Schneider, and he has been building automatic transmissions and converters for drag racers for about 30 years. His shop is in Grass Valley, CA, a few miles North of Sacramento. He has built Torqueflites for many West Coast NHRA racers who have won Divisonal races, National events, and held records... and has built the converters for the $$$$$$$ Dinan twin-turbo V-12 BMWS, and will be building the converters for two of the fifty 2009 Cobra Jet Mustangs that will be "factory hot rods" from Ford, with 700HP supercharged, 4-valve, V8s built for NHRA drag racing. The reason he's only building two is, the other 48 will all be manual trannys.
This guy has been around. The many record-holders that utilize his Mopar transmissions go back to the late '70/early '80s (see attached photo of the Winter/Esslinger record-holding 340 Duster from 1983.)
I said all that to say this: When he talks, I listen.
When I built my supercharged 360 Magnum-powered Valiant, I had to get a transmission, so I asked him the age-old question: "904 or 727?????"
He told me some amazing stuff, the crux of which was, unless you NEED a 727 (700hp and up), you will have better luck with a 904.
Aside from the better e.t.'s afforded by the lighter internal components (he wasn't really very adamant about that), the most important thing he told me is this:
727 Torqueflites have such HEAVY rotating components that if you use stock planetaries, clutch drums, etc., and run rpms over 6,000, they will literally tear themselves to pieces without any help from you. The start/stop operational process that goes on in a Torqueflite places huge inertia loads on the components, over and above what it takes to move the car and control engine rpm. His experience has proven over the years that a properly-built 904 will handle up to 700 horsepower and live. There's no reason to give away that car-length and a half-to two carlengths that a 727 will cost you, for longivity, because it's not going to live any longer, IF as long.
Now, I am sure that there will be guys here, whose experiences will be in direct opposition to what he told me, and I certainly wouldn't argue with any of them; they know what happened to THEM.
I have NO dog in this hunt; I'm just telling you what a guy who makes a very good living building these things told me.
My 904 has taken a LOT of abuse and still is shifting cleanly and with authority, hooked to a blown 360. It won't last forever; nothing does, but I took his advice and haven't been sorry, yet.
The automatics that are the darlings of Comp Eliminator, and are run behind the Hemis in the NHRA's SS/AH class where money's no object, are mostly ProTrans transmissions, which are based on the 904... and some of those Hemis are putting out 800+ HP.
That's all I have to say, except when I asked him about "exploding Torqueflites," something I have heard about, but have never seen, he said that that was a phenomenon of 727's... and was due to the rear sprag anchor coming loose in the case, and was something that just never happens to 904's because the anchor setup is better-engineered. He said he'd never heard of a 904 exploding... in 30 years.
Like I said; these are HIS opinions and information... not mine.
You pays your money, and you takes your choice. Good luck!!! :happy10:
Bill, in Conway, Arkansas
