Anyone running a 904 behind a 340?

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CudaFactHackJob said:
Duane, the springs in the sprag are over fifty years old. They crack and split apart. Then the rollers fall over 90 degrees and get jammed up. The drum is probably undamaged. But the riveted in sprag has to go, so drill out the rivets from the back and the drum will pull out with the sprag.
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You guys realize this thread has been dead for 4 years, right?
 
dibbons said:
The original poster is still here though (me).
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Ok well then we should mention that since this thread was started, you can now buy a 30 element one way clutch. I call it that because it replaces the original roller clutch, but the new design has no actual rollers. They look like little dog bones. Now there will be posters that will say you don't need this, and I cannot tell you why some guys have no trouble with the stock design, and others tell me they cannot keep a stock one from failing. According to ati, the roller clutch is the biggest weakness in the 904 and the new dog one style can take much more torque.
 
Not as far as I know.
What I have read is a certain famous racer switched his 727 to a 904 with winning success up until the others complained and was promptly banned from racing until he dragged the officials down to the local dealer where a car was put up on a lift as to prove it came stock with the car and this legal for competition.
 
rumblefish360 said:
Not as far as I know.
What I have read is a certain famous racer switched his 727 to a 904 with winning success up until the others complained and was promptly banned from racing until he dragged the officials down to the local dealer where a car was put up on a lift as to prove it came stock with the car and this legal for competition.
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I believe those were Canadian cars that were shipped with the 904 but NHRA was not aware of it. Thus the 727 pro trans with 904 internals was allowed. Correct me if I have this wrong.
 
dibbons said:
Well, I recently had the 904 I have rebuilt (Fresno) and asked the owner of the trans shop to install a shift kit. He said he does that anyway, so I just got his "regular" rebuild. It seems to shift very smoothly and very quickly, which I like. The strange thing about the rebuild is the shop gives 3 years or 50,000 mile warranty, which for me is unheard of (i expected something like a 6 month warranty).

Anyway, when I put together the "stockish" 340 I need to rebuild, it will replace the stock '72 318 which is in the car now with the 904. I guess the 340 will go in just the same as the 318, except for one of the motor mount brackets and one of the transmission to engine braces.
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Many are 12 month or 12k.

Where did you go?
 
I have a stock 904 and stock converter that has lived 5 years behind a 360 that makes more power than a stock 340. It has survived fine, and still shifts great. I had new seals/gaskets installed and tolerances checked before I installed it.
  • I've also had them give out behind 318's that were basically stock engines.
 
MoparLeo said:
We always hear the stories of " I use behind bla, bla, bla and never a problem." My dog is bigger, what ever... There are pros and cons to every application. True the 904 has less reciprocating weight, lighter bla,bla,bla...OK The 727 are in normal applications, bullet proof. Most applications. Lets try to talk about what Joe Mopar should expect in stock condition on his application. Yes you can have anything built to withstand anything, but not everybody uses them for racing. A race car is a race car, a street car is a street car. Not the same. A race car only has to do its thing for a very limited amount of time. A street car has to live for a much longer time in many different driving conditions. Not on a track. Either trans will live for a long time in 90% of the typical applications our members will encounter.
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727 Bla Bla Bla , race car only has to do it's thing Bla Bla Bla , Fact #1 nobody has ever had a leg torn off or been killed by an exploding 904 , you will however find thousands of pics from blown up 727's , Fact#2 Most of the top pro racers in the day used to put the guts from a 904 into a 727 case to fool tech inspection and these were 1000hp+ cars , Fact#3 My home rebuilt / upgraded 904 which was the first automatic transmission I ever even looked inside of has been across Canada 6 times and has more than 40k kilometers behind my 410 including a few 10k+ RPM episodes without ever missing a beat or needing a top off .
 
Jadaharabi said:
A&A transmission makes the internal spring kit that you need to replace the factory reverse wound spring. I like working with John cope with cope racing Transmissions that's why I bought the parts from him rather than from a&a that seems to be operated by a butthead.
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I called them, was gonna spend some cash... they just acted like they didn't have time for me, or my questions. Was told to call back for John. He didn't have time either
 
Lame. That oft-repeated statement about herds of blown-up 727s but never a 904 is a pathetically ridiculous statement. The perveyers of this nonsense always FAIL to mention that, while the 727 came in both sb and bb configurations, the 904 NEVER DID. Put a bunch of 904s behind some BBs (You can't cuz they won't bolt up!) and watch how quick they turn to scrap metal.
 
CudaFactHackJob said:
Lame. That oft-repeated statement about herds of blown-up 727s but never a 904 is a pathetically ridiculous statement. The perveyers of this nonsense always FAIL to mention that, while the 727 came in both sb and bb configurations, the 904 NEVER DID. Put a bunch of 904s behind some BBs (You can't cuz they won't bolt up!) and watch how quick they turn to scrap metal.
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Built to the max a 904 will handle 1000 hp
 
Brooks James said:
A and A style, pls educate me
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First thing you have to do on a 904 transmission is eliminate the reverse wound spring in the front clutch. Sometimes they have a tendency to unwrap an that makes for a real mess. So the first part I bought was the spring kit from cope that was designed by A&A.
904 Aluminum Multi-Spring Retainer Kit - A&A Transmissions
Like said above times change you can now get the properly wound spring from ATI I believe it is for about 35 bucks.
Then went with the thicker struts or links for the band went with a aluminum Billet Servo all that good stuff. I believe it was Red Eagle clutches and kohlene steels and a reverse pattern Griner low band apply valve body.
Basically I copied an A&A or a CRT 904 transmission build. With help over the phone from John. A&A just want to sale me parts or transmissions, no technical support. They treated me the same way at Mopar Nationals when I was trying to buy parts from them. So I just put the parts back down and said no thanks and left.
 
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Jadaharabi said:
.
First thing you have to do on a 904 transmission is eliminate the reverse wound spring in the front clutch. Sometimes they have a tendency to unwrap an that makes for a real mess. So the first part I bought was the spring kit from cope that was designed by A&A.
904 Aluminum Multi-Spring Retainer Kit - A&A Transmissions
Like said above times change you can now get the properly wound spring from ATI I believe it is for about 35 bucks.
Then went with the thicker struts or links for the band went with a aluminum Billet Servo all that good stuff. I believe it was Red Eagle clutches and kohlene steels and a reverse pattern Griner low band apply valve body.
Basically I copied an A&A or a CRT 904 transmission build. With help over the phone from John. A&A just want to sale me parts or transmissions, no technical support. They treated me the same way at Mopar Nationals when I was trying to buy parts from them. So I just put the parts back down and said no thanks and left.
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Same deal here. They didn't even wanna help me pick the right parts for what I needed. Guess you have to be a 727 Master Tech to buy anything from them. Unless you wanna just hand over a grand, but less than 2 for a pile of stuff you may or may not really need
 
Yup, you sure can build a 904 to handle 1000 hp...the only thing that beats cubic inches is cubic dollars.
 
Duane said:
Ok well then we should mention that since this thread was started, you can now buy a 30 element one way clutch. I call it that because it replaces the original roller clutch, but the new design has no actual rollers. They look like little dog bones. Now there will be posters that will say you don't need this, and I cannot tell you why some guys have no trouble with the stock design, and others tell me they cannot keep a stock one from failing. According to ati, the roller clutch is the biggest weakness in the 904 and the new dog one style can take much more torque.
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I'm going to chime in here and watch the haters come out (lots of them on here now). I realize this is an old thread, however I've been off this site for almost 2 decades.

The multi-element, cam style, dog bone 904 sprags do not work. Do not install one--it'll cost you several thousand dollars in damage when it fails. Ask me how I know.

The stock 904 sprag does not like a lot of torque, big tires or tire shake. So, you need to take these things into consideration when planning a 904 build.
 
Duster346 said:
I'm going to chime in here and watch the haters come out (lots of them on here now). I realize this is an old thread, however I've been off this site for almost 2 decades.

The multi-element, cam style, dog bone 904 sprags do not work. Do not install one--it'll cost you several thousand dollars in damage when it fails. Ask me how I know.

The stock 904 sprag does not like a lot of torque, big tires or tire shake. So, you need to take these things into consideration when planning a 904 build.
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What is your suggestion for an upgrade for the sprag?
 
There really isn't an aftermarket one at this time. There are people that are working on it or plan to work on a better design.

I am limited on what I put a 904 into as there are several factors involved, as I've stated.

The best factory 904 sprag is the 1989-1993. It's a 12-element caged bolt in design. But it is specific to the 1989-1993 lockup cases, if you can find one. The L/R drum has a snap ring that retains it to the output shaft support, and there is not an option to add needle bearings in that L/R drum and support at this time--which is the only downfall.
 
John Cope built my 904. It has been in my 71 Swinger for over 10 years. 408 stroker making north of 500 hp has not shucked it yet.
 
Duster346 said:
I'm going to chime in here and watch the haters come out (lots of them on here now). I realize this is an old thread, however I've been off this site for almost 2 decades.
Ok how do you know. What doesn’t work?


The multi-element, cam style, dog bone 904 sprags do not work. Do not install one--it'll cost you several thousand dollars in damage when it fails. Ask me how I know.

The stock 904 sprag does not like a lot of torque, big tires or tire shake. So, you need to take these things into consideration when planning a 904 build.
Click to expand...
 
Duster346 said:
There really isn't an aftermarket one at this time. There are people that are working on it or plan to work on a better design.

I am limited on what I put a 904 into as there are several factors involved, as I've stated.

The best factory 904 sprag is the 1989-1993. It's a 12-element caged bolt in design. But it is specific to the 1989-1993 lockup cases, if you can find one. The L/R drum has a snap ring that retains it to the output shaft support, and there is not an option to add needle bearings in that L/R drum and support at this time--which is the only downfall.
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There is also a larger diameter sprag in the late 80,s 999 that does not use that snap ring on the drum.
If you order the 30 element roller clutch from ati, they will ask you what diameter.
 
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