904 tricks?

[chargersrule]

I've talked to people who have said they reworked their valve body by enlarging holes and shiming springs and things, I was wondering where I could get more informationg on this. Anything will help as i'll be racing soon. thanks

[John Kunkel]

If you're going to be doing some serious racing, spend the money for a full-fledged reprogramming kit like the B&M Transpack, TransGo TF-2 or TCI Trans-scat.
Simply drilling holes and shimming springs won't accomplish what these kits will do.

[Dart]

The best dollar spent on a 904 is to replace it with a 727 especially if you are mainly street driven. A hardcore race 904 will only last about 50 passes before having to be rebuilt. Even if you use the beef internals. You would only lose .02 between the 904 and the 727 and the 727 is markedly better.

[70AARCuda]

Been racing a 904 for 8 or 9 years....has not been rebuilt ....but will finally rebuild it this winter. Probaby has a 1000 or so passess.

1000 divided by 50 is about 200.. so i should have rebuilt the trannie 200 time by now...dam...i must be missing out on something.

69 barracuda
360 +0.60 with w-2 heads.

ran a best of 10.62 @ 124 in vegas heat.

last 3 yrs has a set of standard heads....ran best of 11.25 @118..

Did i memtion i have been using a Tranzact transbrake all those years also?????

Have someone who knows what they are doing rebuilt the 904....and you will be OK....and skip the other 199 rebuilts...

thanks

tony

[Mister Fiberglass]

NOT a damn thing wrong with a 904........HELL - they use them behind some SS hemi carz !!

JUST get a good valve body and use good parts....clutches and bands.

[bwlizard]

Originally posted by 70AARCuda
1000 divided by 50 is about 200.. so i should have rebuilt the trannie 200 time by now...dam...i must be missing out on something.

OK this is the new math right ? You are missing something !

[skankweirdall]

Originally posted by bwlizard


OK this is the new math right ? You are missing something !

Shame on you 70AARCuda, you should have rebuilt it 20 times by now.


I run a 904 in my 3000LB.+ car with a T/A tranz brake. No problems. I've been opening it up and inspecting and refreshing every winter, though it's not necessary. Just peace of mind for me and a way to stay out of the house.

[hemivaliant]

I'm running a 904 in my street and track driven A-body. Never had a problem with it. The car was put together in '95. If I used that new math it should have been rebuilt hundreds of times by now. It hasn't been rebuilt since it was put in the car back in '95.


HV

[Mister Fiberglass]

HELL....I furrgot to mention - I have a bud in FL who has a 4000 lb PLUS stock eliminator car that runs in the 13's that has had the same 904 in it for over 12 years..........

[chargersrule]

i guess i left the most important stuff out. You guys are getting the wrong idea, this is gonna be for a 78 dodge aspen beater that i'm gonna run nitro on at the track(in the tank RC stuff).
I have a fully manauly valve body and a 3,000 stall speed converter and a freshley built 904 that i was gonna use in the charger, but i'd like to keep that until i get a small block in the car and putm both in at the same time.
Right now i'm running a slant six that might get hedders and triple dueces, Anways, i'm pretty broke right now, have an extra valve body from a parts 904 and am looking for very cheep ways to not look so slow at the track, thanks for all the help so far thouhge.

[Jack Z]

chargersrule:

I don't mean to get off of the 904 transmission subject and I'm not trying to be a party pooper here, but you say that you're going to run RC nitromethane fuel and that "I'm pretty broke right now"????

You'd better get ready to be "DOUBLE EXTRA pretty broke" if you plan to run enough nitro to show a significant performance gain in a relatively stock slant-6 engine!!

[70AARCuda]

Sorry about that math...actually i am very good in math..since i work in engineering field.

Besides it was late at night...It just burns my shorts went someone says the 904 is no good..get a 727...thats all...........

thanks

tony

[John Kunkel]

If you like math, consider this:

The friction lining surface area on a 904 clutch disc is exactly half of that on a 727 disc and the surface area of the apply piston is larger on the 727 so, at equal hydraulic pressure, the 727 clutch applies with more pressure.

The 904 kickdown band has 53% of the lining surface of the 727 and the 727 servo is larger so, with the same hydraulic pressure and lever ratio, the 727 band applies with more pressure.

The 904/727 debate can be likened to the choice of a clutch in a 4-speed car. A 9" clutch will weigh less and have less parasitic loss than a 10 1/2" but the difference comes down, plain and simple, to the ability to transfer torque without slipping.

Would anyone here consider running a 9" clutch in their race car?

[Mister Fiberglass]

Interesting figures there JK and food-for-thought.

But how are there any parasitic loses in the diff between a 9 and 10.5 clutch disc besides the little bit of additional weight ?

[skankweirdall]

There is no doubt that the 727 offers more friction surface and superior holding power, the question is though, does the 904 provide adequate holding force and friction surface area? This I believe it does and the 727 becomes overkill for many applications.

It's a bit different than trying to launch a static car with sticky tires and lots of torque at 6000+ RPM's.

[Mister Fiberglass]

Originally posted by skankweirdall
There is no doubt that the 727 offers more friction surface and superior holding power, the question is though, does the 904 provide adequate holding force and friction surface area? This I believe it does and the 727 becomes overkill for many applications.

It's a bit different than trying to launch a static car with sticky tires and lots of torque at 6000+ RPM's.

GOOD point ! ....... but I think that it depends on what the car combo IS. I have got a footbrake dragster project and I will be eventually adapting a complete 904 trans to a B engine to SEE for myself ...........how it will perform in a very lightweight, decent aero car.

[73challenger360]

any recommendations on a 904 planning on running 1 in a 1973 challenger with a 360 with about 400hp or so

30 over
484 284 purple shaft
2.02 J heads
rpm air gap
750 mech demon
forged pistons
moly rings
balanced
b&m balanced flex plate

still need to purchase radiator, rocker arms and tranny, torque converter

any thought on ger, mancin racing , tci trannys

going to go with comp 1.5 adjustable roller tips

any thought on any of this would be appreciated

dang thing wont fit under the hood!!!!

[Mister Fiberglass]

how heavy is the car? how big of a gear?

[dwc43]

GER conveters and such are junk. Dont waste your money on that stuff. Mancini's o.k. TCI converters and trans are the way to go. HEY, who needs a hood? Just extra weight right??

[73challenger360]

3.55 gears
approx 3500 with driver

[Mister Fiberglass]

a 904 should work OK BUT.......

are you starting off with the combo? do you have access to a 727?

[73challenger360]

planning on a gear venders under overdrive in 12-18 months the 3.55 rations will be 2.77 final drive

anybody know anything about the procharger system I was sent some imfo and its all for chevy crap all I know is it is about 4300 bucks with cooler, good for 8lbs. on 9.0to 1 cast iron heads

[Mister Fiberglass]

plans for GV OD ?....... you will have to go with a 727.

[73challenger360]

why do I have to use the gear venders they make a 904 kit

[Mister Fiberglass]

Again?

[73challenger360]

I don't get plans? Its and overdrive

um I live 20 minutes from Pheonix the speed limit on the freeway is 75 and I don't want to turn 4000rpm in 120 heat

[skankweirdall]

Let me just say this. I would not recommend a 904 for a heavy street car. It would probably hold up, but why bother. The reason to use the 904 is it's lighter and requires less horsepower to turn. There is a tradeoff as to longevity and durabality here so what would be the use in a street car? In a racecar it has it's purpose, but if you are starting from scratch I'd go the 727 route, or if you don't mind doing a little surgery on the tunnel and crossmember go with a 518, then you already have the overdrive.

[FASTDARTCHESTER]

yep, 727 has more frictional surface grab, but also more weight to stop when bands grab. aren't outer diameters of the clutches bigger too? this equals higher rotational velocities to slow/stop...

904 also has 2 flavors of kickdown band width. rigid band will take a wear pattern and normally grab evenly. I swear by Kevlar for the kickdown band (it is a superior material).

the 904, in my opinion, is just as good as a 727 for draggin. i have had great luck with the 904. YOU JUST NEED TO PUT THE THOUGHT INTO BUILDING IT CORRECTLY. most failures are due to improper building.