Maximum HP in 904 Transmission With the following parts:

70aarcuda said
I have using the same 904 since 1993 with a transbrake, it has been rebuilt once in 2004 when the ring gear broke and took out the rear spraq.

On the rebuilt i used red alto clutches and kolene steels, the front clutch has been modified to carry 5 disc...I use keval bands ...a 5.0 band apply lever,,,'
the front clutch pac also has the 24 spring kit instead of the large wound spring...
and i am using a Transzact Pro brake I bought in 1993...

So you guys Who SAY they wont work are correct....

Also my 71 Dart 360 with eddy heads has a 904 with stock clutchs and steels...but again modified to carry 5 disc...and same bands...same 24 spring kit...5.0 lever...and Tranzact Pro brake...It has 4 seasons of racing on it...

both trans use the aluminum plantaries .....they are 904s not the 999

the rear servo in both trans are the Sonax replacement servo which i think cost about 12 dollars....not a high dollar billet item..

So that 904 does not work either...please ship any unwanted 904 to me...

69 barracuda runs in 10.70s ...and the dart ran 11.06 in MATS In VEGAs...

Amen brother, I couldn't have said it better. You take all the 904s west of the Missippi and I'll take all of um east. Once again, I bring up Bucky Hess. He used to run the 904 in his Super Stock '68 HEMI Cuda. That car was well in excess of 800 HP. Course, it had a bunch more done to it than the OP is talking about, still they can be made to withstand boocoos of power with the right parts. To the OP....I agree with whomever recommended a good cooler. THAT will be the life of it. With the mods you mentioned it will be fine at that HP level. Also, along with the servos mentioned, you want to upgrade the kickdown band actuating arm as well. They can distort under severe stress. Mopar Performance makes a fine replacement, on the cheap.

Oh and to 70aarcuda.....how come you're moddin direct drums for five clutches? The A-500 comes with a 5 clutch direct drum and will fall right in the 904......unless you're usin somethin billet or aluminum? You can also get the 4 disc forward drum on the cheap from wittrans. check out their site. Great prices. https://www.wittrans.com/default.aspx