Here goes...My '56 F-100 project is getting a Blown 331 Hemi for power...real mild cam ...5 lbs. boost...set-up for performance but not racing (maybe 400 HP?). I've got a nice Mopar 904 transmission with a 2000 stall converter...just rebuilt...Alot of hot 340's used these 904's and they seemed to work fine. Do any of you transmission experts have an opinion on why I have to use a 727? Hell, I'm using a 9" with 28 spline axles so if I trust the 28 splines I should be OK with the 904...I need an opinion. Thanks.
The 727 is stouter, but the 904 is a good tranny and lighter. I don't see 400hp as a problem for either.
I run a 904 in my slant 6 Dart drag car. It has an extra set of clutches, a reverse pattern valve body and a 3000 RPM stall convertor. I just had the transmission rebuilt but the old one just like it had run on the strip for about 10 years. I know that my motor does not put out the power that you are but I do work the transmission hard. Its best run has been a 14.2 but I have not made a pass that good yet.
You might want to have the 904 beefed before you put it in, or you'll wind up having to take it out to have it beefed when it smokes a clutch pack.... Blower motors are fun!
The 904 will handle it.The drag car I helped with is a Dart with a build 318 that runs mid 12's and we beat the piss out of it for the four years never a problem. You might want to have a pro build converter made for it that made a big differance in our car.
I had a 727 behind my blown 392...They said it would handle 800HP. I am sure the 904 would be fine for your engine though. -Jason
i've never broke a 727, even after maybe 500 hard passes in one of our race cars. and the only 904 i've ever broke was after 300,000 miles in a daily driver. i think a well built 904 ought to handle that hemi. David
I've got a local who will re-do the trans with a performance rebuild...I used to do automatic's back in the 60's but haven't done one since...better let the pro's do it. Thanks for all the input...I thinks it's gonna be OK.
We build converterless 904s for the roundy round boys & they hold up real well. As someone else said tho, go for a top shelf converter. I can vouch for four-thirteen, we seen him make about half of those passes at HAMB drags. It was one of my favorite cars there. DAVE
NHRA class drag racers often prefer a built 904 over the stouter 727 because they take less horsepower to turn.
I used to be a transmission wrecking machine. I've broken nearly anything out there. I can honestly say the only problem I ever had with a 904 was converter related, and that happened to two different 904s. The first was in a 68 Charger with a stout 340 and a 3:55 sure grip. I was pretty brutal on it, the inside of the converter came apart and covered everything inside with alumium. The second one was a few years later in a street rod with a 360 and 3:23 gear suregrip. That converter also came apart and spread the alumium inside. I have also seen several with cracked converter hubs. Must be the weak point? Gene
I've never had a 904 behind something more than a slant 6, well there was one behind my 318 in my RR but I never drove it that way. Like was said earlier more drag guy's are using the 904 because they are lighter and have less rotating mass to over come. I just got done rebuilding a 727 for a friend of mine and he was askin the same thing about them. Try A&A transmission out of Indiana, they have been making parts to beef up the 904's for a while. I believe they make converters for them also. The address is A&A Transmission 9699 W.County Line Road Camby,Indiana 46113 I purchased a bolt in rear sprag from them for my 727 when I rebuilt it. Hope this helps,later plmczy
I've had both, and always had better luck with the 904, believe it or not! The 904 is lighter, smaller and (pay attention!) takes less power to operate...which means it also builds less heat...making the car go faster while the tranny lives longer! With a 400hp engine, a properly rebuilt 904 will barely be breaking a sweat...trust me. As others have said...a GOOD converter is CRITICAL here...Chevy guys can get away with cheapies...but you don't wanna try that with a Tourqueflite! Probably better than half of all failures involving Chrysler automatics in performance useage can be traced back to a cheap or faulty converter! (With insufficient cooling and improperly adjusted throttle valves running a close second!). Pay attention to the details, and the trans will live a long time and serve you well.
I'm having a "streetable" Slant built - nowhere near the HP that your Hemi will make.. and I have a freshly rebuilt 904 to go behind it. The guy that rebuilt it upgraded it with the heavier duty parts that the 904s in V8 cars use... I didn't get details about exactly what parts he was changing, but I can ask him if you like. Lets see some pix of that Hemi!
I rebuilt (failed seal in a clutch pack) a 904 once, and installed a B&M shift kit. I think I used the "heavy duty" style of the kit. When I finished the job, I realized that at the end of the process I had used NO parts from the selection in the kit except for a single soft plug--all the mods for this version were drilled holes, discarded springs and balls, and adjustment of the line pressure! I carefully measured the plug and kept the instructions and pressure adjust gauge, and that's all that's needed for further shift kitting.
Man , you guys have really come thru for me...any questions I had have been answered from HAMBer's with actual experience and that's a real plus...Now all I have to do is get my cheap-ass Samsung camera to download and I'll send some pix of this project...Thanks for all you help ( and future input)!
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