How about a good Drag race 904 build discussion

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Duane

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I am just going through my custom built by me rollerized 904 and am contemplating some possible changes.
I currently am using four pinion steel planets.
Has anyone used a three planet rear planetary with a brake and some significant horsepower.
I also run an aluminum front drum.
Anyone who has built their own trans care to share some specifics about the internals of their build.

Duane
 
Don't need anythign special, no alum front drum or much of anything else.

A good servo set up, multi spring for drum, good clutches and seals... that's about it.

There have been multiple threads about building these with parts list that people have used.
 
What is the advantage of using this type of spring. I was not talking about a basic rebuild.
This thread was supposed initiate a technical discussion.
For example should you install all 24 springs or less.
Anyone using 3 pinion aluminum planetaries.

Duane
 
I have not seen this product anywhere else. There is quite a substantial weight savings by using these pressure plates. I would think that using them in the rear clutch would be ok as this is not a shifting clutch. Would there not be minimal slippage here just when putting the car into gear?

Duane
 
why would you want to use 3 pinion and aluminum if you already have 4 pinion steel.
 
Duane said:
What is the advantage of using this type of spring. I was not talking about a basic rebuild.
This thread was supposed initiate a technical discussion.
For example should you install all 24 springs or less.
Anyone using 3 pinion aluminum planetaries.

Duane
Click to expand...

The single wound spring will unwind in high rpm and cause the clutch disc to drag...the multispring kits solves that problem
 
Hi Fred. The reason I asked about the 3 pinion is that I have one here and it is significantly lighter in weight which would equate to a lower et. Just like aluminum drums improve et because of less rotating weight.
The concern I have is if it is strong enough with only 3 pinions. I believe that a member on here
Named Valiant Steve once told me that he used 6 cylinder planets in his 904.
I believe I had heard that the rear planet receives less load than the front planet.
I recently overhauled the 47 re in my diesel truck and from the factory it came equipped with a five pinion steel front planet and an aluminum 4 planet rear planet.

Duane
 
True, the 47 series diesel transmissions had 4 pinion aluminum rear planets and can handle some decent power, albeit under 3500rpm usually. I have to wonder though if it is that significant of a weight difference to make any change in ET in a car application. What RPM do you shift at, and go through the traps at?
 
Are you sure a 47RE or 47RH rear planets going to fit a 904?,,,,,

Those trans are based on the 727......
 
I was just making the comparison that chrysler themselves place more emphasis on beefing the front planet than the rear one. So my thinking is that " maybe" the 3 pinion aluminum 904 planetary would survive and also shed some et as well. The et gain may be small. But small gains here and there can accumulate.
I used to run a 727 in my car with nothing more than a T/A cheeta valve body.best et 11.70
I put in a 904 fully build with aluminum front drum lightened sun shell 2.74 first gear and fully rollerized and a little more converter stall speed. Best et 11.20.
The point of this thread is I wanted to find out if anyone else has tried some other 904 mods.
I have not tried any decent servos in my 904 yet. I have just installed the multi spring return
Spring. Man is that spring stout.
My experience is that there is significant performane to be gained from the transmission.
But it is a fine line between et gain and durability.

Duane
 
Duane, look at what is offered by the known RACE trans builders. The few I've seen for 904 TransBrake applications all had 4 pinion steel with roller bearings, not the oem thrust washers or any Aluminum 3 pinion planets.

Whats the quickest you've seen or heard of running a 904?
 
Ask 70AAR to list a link or parts he uses in his trransmissions. He's got at least 3 904, transbrake deals in use and some have a LOT of passes on them. Look at the times in his sig. All are 904's.

Mad Dart is throwing a lot more power at a 904 than you have and he used the same stuff.

I know of a couple 904's that run very low 9's at 2800-3000 pounds. Nothing high dollar in any of them.
 
TCS along with actually making a lot of the custom goodies they sell also run a 1400hp Comp Eliminator car with a 904 in it so they definitely know what they are doing , I used their race rebuild kit with the billet steel from drum and 24 spring kit because my car is mainly a street car and the aluminum drums don't last on the street but if you wanted tech help they have always answered my calls and been very generous with their time and knowledge .
 
I have seen plenty of 9 second cars using a 904s.
My prediction is that the 904 is headed the way of the power glide in terms of aftermarket development. I don,t know how to post a link, but I just recently read an article about ATI recently developed a new roller clutch exclusively for the 904 that can take up to 1500 ft pounds of torque. They claim that the roller clutch is the 904s most unreliable component in big horsepower applications. I just recently received my w2 heads back from shady dell speed shop and I would expect very similar performance from my 68 dart that 70aar has in is cars.
I bet the combinations are very similar too.
One of the big trans builders claims on there web site that the 904 is one of the biggest drag racing secrets out there. Looking at tcs I am surprised at the amount of aftermarket support for the 904. Apparently some of the hemi superstockers are using the 727 with 904 internals.
But I here that durability is 8 runs. Yes I would very much like to see a parts list of the trans in 70aars 904. Am I spelling that right lol.

Duane
 
Look above at post 14...and click on link...Mad Dart has listed everything you need...

the Pro-file is basically a 904 trans...they use the AMC bellhousing cause it is larger and allows for better selection of converters...

everything in the 904 Pro-file is custom made and billet....they sell for around 6k......
 
Why go to the trouble of rollerizing an aluminum 3 pinion planetary if there is no application for it. Thanks for some of the links guys. Good info there. Fred yes I have heard that in a trans brake application you must use the rollerized support for durability, but I am curious what a & a trans says is a suitable application for a 3 pinion aluminum planetary.

Duane
 
rollerized support for transbrake...****....I got one 904 that has had a transbrake in it since 1993.....and it aint got no rollerized support..
 
Many builders claim that the stock support will gall in high load transbrake application. But hey if yours works it works. I put the rollers in for decreased drag and believe me the roller bearing deal gets rid of a ton of friction. Takes a lot more brake effort to slow down after a run. Just parked in my driveway it will roll effortlessly.
I would never argue with someone who has a successful running car. Just reporting what I have heard and my own personal experiences. That was point of this thread.
I guess part of it is if a person is happy with the performance level of there car and if it's reliable. I am looking for more performance, closer to where your cars are. Some of it is to be found in my engine , perhaps some in my trans.

Duane
 
I ordered the new tf904 multi element roller clutch today from ati transmission.
According to there tech tips in the product manual, for every pound of rotating weight removed from a transmission results in 7 more horsepower at the rear wheels.

According to ati the new roller clutch was developed for the new drag pack challengers when they came out. It was determined that the target performance of about 10.50 second et in these cars was the performance level that the stock 10 roller clutch would become problematic.
(Read break).
The clutch was developed by ati with the blessings of chrysler. Ati fulfilled the drag pack challenger orders for chrysler and then made the clutch available to the general racing public by special order only. I had to authorize payment up front and the order will take two weeks to fulfill. I have seen a few torqueflite explosions over the years and Safety and reliability are important in racing. I feel that using this new roller clutch with an aluminum or billet steel front drum should all but eliminate the possibility of failure, especially with foot brake racing with a valve body that does not apply the band in 1st gear.

Duane
 
Seen a few tf explosions....904s?

Got 3 transbrake 904s in use...none are LBA valvebodies...one since 1993....

Did I miss the memo?
 
70aarcuda said:
Seen a few tf explosions....904s?

Got 3 transbrake 904s in use...none are LBA valvebodies...one since 1993....

Did I miss the memo?
Click to expand...

I forgot to send you the memo that 904's don't explode like 727's... sorry. LOL

This isn't a discussion. It's taking just about everything anyone that's actually built and raced using a primarily stock hard parts 904, discounting it, and spending untold $ on parts that are overkill for a 10 second and slower car.

Visa, It's everywhere you want to be... CHARGE! :cheers:
 
I asked ati what the intended performance level of the clutch was aimed at without them knowing my performance level. They indicated to me that mid to low ten second and lower.
You are free to disagree with the Chrysler engineers if you like.
An aftermarket 727 bolt in clutch has 16 rollers. The 904 that I have has 10.
As I understand it the 727 has more failures because the stock clutch is a pressed fit and can potentially spin in the housing. The 904 is riveted in place so probably will not fail that way.
The issue with the stock 904 is roll over because only ten rollers to take the load.
I would think that there is more load on a 10 second 3000lb car than 10 second 2700ilb car.
Even if you don, t explode a drum. You could still break the clutch from a driveline failure.

Duane
 
I have a saying. Pick your part, pay your money.

Based on some of your comments, you don't have a clear understanding of the failures, causes and things to look out for. All of them are primarily 727 issues.

Some people spend money on stuff that will provide ZERO benefit. Do I care, nope. If you have budget constraints, the money you spent on that high dollar sprag ~$350 and drum ~$600, could have been better spent on a quality converter. Just don't complain when someone with a "junk" parts 904 and great converter kick your tail for under $800-900, less than your two parts alone. A lower cost alternative that sprag is a low band apply valve body.

People will sell you whatever they think they can a lot of times. Are the parts better, yes. Are they necessary... HELL NO. Some will buy the "trick" of the week. you can roll that high dollar piece too. You don't like the answer you got, have at it. I think you wasted money.

Some of the heavy cars I know that run 904/brakes with all stock drum/sprags

10.52 128 3350#
10.38 130 3400#
10.65 126 3400#

Then there are Tony's cars coming in at 2850-3200 or so.

Like I said this isn't a discussion, you already made choices regarding parts you THINK will benefit you and you are looking for a pat on the back to say you did good. I know that two of us in here aren't going to do that.

Build your stuff and run it.
 
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