904 race tranny Recipe

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dusmon

dusmon

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Ok Thanks in advance for the help.
Looking for what parts to use to build a 904 for behind my 416.
Car has 31x13 rubber 4.56 gears @ 2900# with driver
Will run in the 10's.

So with the knowledge here let me know what parts to get.
Torque converter-
Valve body-
Year of 904-
Clutches-
Bands-
Planetary-
Seals-
 
Ok I'll re'ask the question what is everyone else running?
As im looking at what parts to buy.


Year of 904-
Torque converter-
Valve body-
Clutches-
Bands-
Planetary-
 
What you want to look for is an A999 transmission. These were the 'heavy duty', non-lockup versions of the 904 that generally came behind pass cars with 360s in the mid-'70s. '(74-'78) The difference between a regular 904 and the 999 is the 5 clutch drum. Garden variety 904s generally came with 3 or 4 clutches. Find a low gear planetary set from a later 904 (early '80s) and you're golden. If you have more cubes though, it may not necessary to have so much torque multiplication in the drive line.

Unfortunately though, finding a 'real' A999 is very difficult because they are rare as hen's teeth. Plus, even if you do find one and the case has the right number, there's no way to verify what's inside until you open it up since they are the same externally as a regular 904. You can build them from scratch but you need to be aware of specific parts and how they work together. That is a lot of work in itself.

I have two 999s. One is a spare and one in the car right now. I also have a low gear planetary set on my shelf. They are great transmissions and can be built to the moon with all sorts of high-dollar parts.

They respond to modifications like a a 727. The main advantage of the 904 is less rotating weight in the gear train which helps to prevent explosions. It's rare to hear of a 904 blowing up but a 727 is like a ticking time bomb with the steel front drum.

Here are some threads from Moparts about 904/999 race transmissions, should tell you all you need to know.

Everything you never wanted to know about 904s.

Racers/builders.

How to identify a 999 from a 904.
 
You don't need to go all crazy for a 904 to handle the power you are going to be putting through it. Just remember that. People get all caught up in all these exotic parts etc when it is not necessary. If you want the low gear set that is your choice. I have a a999 that is tore down in my shop right now that has the Low gear set but it only had 4 clutches in the front drum. So take that for what it is worth.
The 904 that I built I copied and used the parts that were recommended to me from guys I know that have been successful racing. The parts I was told to use will easily handle more than most would ever put through it. From how hard they run their cars I do not doubt them for 1 bit. Cost of parts was somewhere in the $500.00 range not counting the Valve body or Converter. This was the first one I have ever built and I probably got maybe 6 Hours total into it from tear down to painted…. Done.
What you will find out is when you go to get the parts, no single vendor will have them all. I would also say stay away from the BIG name brand guys because they will for sure take all your $$ for the exact same thing you can get down the street for a lot less. There is no magic to building one of these transmissions but most will try and brain wash you & will try to get you to believe different.

Also there is no need to find a certain year transmission for the 5 clutch front pak. Use the thin Reds and steels to make your own 5 Clutch front Drum. This is what I did. Simple easy.

This should be plenty of info on where to get the parts and at least get you started.

Pump Gears** $36
http://www.tcsproducts.com/products/product/13/

24 Spring* $105
http://www.tcsproducts.com/products/product/15/

Billet Strut* $19
http://www.tcsproducts.com/products/product/618/

Rear Kevlar Band* $18
http://www.oregonperformancetransmi...OD&Category_Code=904&Product_Code=PTB-12820AK

Kevlar front Band $19
http://www.oregonperformancetransmi...D&Category_Code=904&Product_Code=PTB-12905F-K

Servo** $17
http://www.oregonperformancetransmi...ROD&Category_Code=904&Product_Code=SNX-22912A

Makco 904 page.* thin clutches/steels & Kits
http://www.makcotransmissionparts.com/A904.html

WIT trans, teflon seals, trans exploded view
https://www.wittrans.com/search.aspx?SearchTerm=12175ct
https://www.wittrans.com/Schematic.aspx?Transmission=A904

Valve body of your choice and Lever to match.
http://tranzactofindy.com/index.html

Converter…. Call a good vendor and have it custom made for your application.
Lenny at Ultimate has xlnt customer service and does great work.
http://www.ultimateconverter.com
 
If it was me - replace the high gear clutch drum with the billet aluminum big piston, 727 spring type version, get the bolt in sprag, a valve body, a good cooler, and the rest is basically good frictions and stock parts.
 
dusmon said:
Ok Thanks in advance for the help.
Looking for what parts to use to build a 904 for behind my 416.
Car has 31x13 rubber 4.56 gears @ 2900# with driver
Will run in the 10's.

So with the knowledge here let me know what parts to get.
Torque converter-
Valve body-
Year of 904-
Clutches-
Bands-
Planetary-
Seals-
Click to expand...

Dynamic 4200 stall
74 904
Red Alto clutches
basically Cope racing sells the rebuild kit

low 1st gear and Full Reverse Valve Body
4.2 lever
 
There is an ad on Moparts for a street/strip 904 back in October, it's still active until the 15th. I actually thought about snagging this for myself but I don't have a need for it. This is probably what you're looking for. You're not going to get a quality build from scratch for much less unless you have the parts and do it yourself.

Here's the ad text:

904 street/strip trans Small Block Mopar

904 street/strip trans
76- 904 street/strip trans
Just rebuilt no runs or start up
New T/A Rev. manual valve body W/ special spring to boost line pressure
Stock Drum Fitted w/5 Alto red clutches and kolene steels,seals,gaskets,bushings
All new springs,rollers in factory sprag
Modified rev.piston,oiling system,front pump
No gov.,deep pan,5.0 lever
New high gear kevlar reinforced flex band,New Double Wrap rear band
New CRT spring pack,Reinforced band strut
4-pinnion steel planets
PRICE REDUCED $ 1,050.00 + shipping.
1yr. warranty with trans.................................
Thanks Stan. !!!!!WILL PAY HALF THE SHIPPING IN U.S.
[email protected]
 
Mad Dart said:
You don't need to go all crazy for a 904 to handle the power you are going to be putting through it. Just remember that. People get all caught up in all these exotic parts etc when it is not necessary. If you want the low gear set that is your choice. I have a a999 that is tore down in my shop right now that has the Low gear set but it only had 4 clutches in the front drum. So take that for what it is worth.
The 904 that I built I copied and used the parts that were recommended to me from guys I know that have been successful racing. The parts I was told to use will easily handle more than most would ever put through it. From how hard they run their cars I do not doubt them for 1 bit. Cost of parts was somewhere in the $500.00 range not counting the Valve body or Converter. This was the first one I have ever built and I probably got maybe 6 Hours total into it from tear down to painted…. Done.
What you will find out is when you go to get the parts, no single vendor will have them all. I would also say stay away from the BIG name brand guys because they will for sure take all your $$ for the exact same thing you can get down the street for a lot less. There is no magic to building one of these transmissions but most will try and brain wash you & will try to get you to believe different.

Also there is no need to find a certain year transmission for the 5 clutch front pak. Use the thin Reds and steels to make your own 5 Clutch front Drum. This is what I did. Simple easy.

This should be plenty of info on where to get the parts and at least get you started.

Pump Gears** $36
http://www.tcsproducts.com/products/product/13/

24 Spring* $105
http://www.tcsproducts.com/products/product/15/

Billet Strut* $19
http://www.tcsproducts.com/products/product/618/

Rear Kevlar Band* $18
http://www.oregonperformancetransmi...OD&Category_Code=904&Product_Code=PTB-12820AK

Kevlar front Band $19
http://www.oregonperformancetransmi...D&Category_Code=904&Product_Code=PTB-12905F-K

Servo** $17
http://www.oregonperformancetransmi...ROD&Category_Code=904&Product_Code=SNX-22912A

Makco 904 page.* thin clutches/steels & Kits
http://www.makcotransmissionparts.com/A904.html

WIT trans, teflon seals, trans exploded view
https://www.wittrans.com/search.aspx?SearchTerm=12175ct
https://www.wittrans.com/Schematic.aspx?Transmission=A904

Valve body of your choice and Lever to match.
http://tranzactofindy.com/index.html

Converter…. Call a good vendor and have it custom made for your application.
Lenny at Ultimate has xlnt customer service and does great work.
http://www.ultimateconverter.com
Click to expand...

Got 4 904 racing and they are basically done this way....I use Transbrakes from Tranzact of Indy....

Some had low gear sets in them...some did not....depends on car combo.....a small engine heavy car will want the low gear set....or if you can not run alot of gear in the rear..the low gear set can make up for that somewhat.....

The 71 Dart 360 in my signature is bascially making 500 hp based on its weight and performance...and it has a 904 with 5 stock clutch disc in a 4 disc front drum......you dont need aluminum drums...the 904 is not prone to exploding like a 727 due to the smaller mass of the drum....the 904 sprag is riveted into the case not pressed in as the 727...so you dont need a bolt in spraq....you can change out the roller and springs for 5 bucks....
 
I forgot to mention I replaced the parts on the sprague that you can.

1) Rollers, springs and Race with new stock gizmo's. Yes about $5.00

I also agree, the front drum does not need to be replaced with a Billet aluminum or Steel with the 904.
727 Different story.

I was told that the 904's front drum will explode just like the 727 and there was a guy that posted a couple pictures of 1 but it turned out to be a 727……LIAR!! Lol….. I did research for hours and have not found evidence or proof of this at all.
 
Mad Dart said:
You don't need to go all crazy for a 904 to handle the power you are going to be putting through it. Just remember that. People get all caught up in all these exotic parts etc when it is not necessary. If you want the low gear set that is your choice. I have a a999 that is tore down in my shop right now that has the Low gear set but it only had 4 clutches in the front drum. So take that for what it is worth.
The 904 that I built I copied and used the parts that were recommended to me from guys I know that have been successful racing. The parts I was told to use will easily handle more than most would ever put through it. From how hard they run their cars I do not doubt them for 1 bit. Cost of parts was somewhere in the $500.00 range not counting the Valve body or Converter. This was the first one I have ever built and I probably got maybe 6 Hours total into it from tear down to painted…. Done.
What you will find out is when you go to get the parts, no single vendor will have them all. I would also say stay away from the BIG name brand guys because they will for sure take all your $$ for the exact same thing you can get down the street for a lot less. There is no magic to building one of these transmissions but most will try and brain wash you & will try to get you to believe different.

Also there is no need to find a certain year transmission for the 5 clutch front pak. Use the thin Reds and steels to make your own 5 Clutch front Drum. This is what I did. Simple easy.

This should be plenty of info on where to get the parts and at least get you started.

Pump Gears** $36
http://www.tcsproducts.com/products/product/13/

24 Spring* $105
http://www.tcsproducts.com/products/product/15/

Billet Strut* $19
http://www.tcsproducts.com/products/product/618/

Rear Kevlar Band* $18
http://www.oregonperformancetransmi...OD&Category_Code=904&Product_Code=PTB-12820AK

Kevlar front Band $19
http://www.oregonperformancetransmi...D&Category_Code=904&Product_Code=PTB-12905F-K

Servo** $17
http://www.oregonperformancetransmi...ROD&Category_Code=904&Product_Code=SNX-22912A

Makco 904 page.* thin clutches/steels & Kits
http://www.makcotransmissionparts.com/A904.html

WIT trans, teflon seals, trans exploded view
https://www.wittrans.com/search.aspx?SearchTerm=12175ct
https://www.wittrans.com/Schematic.aspx?Transmission=A904

Valve body of your choice and Lever to match.
http://tranzactofindy.com/index.html

Converter…. Call a good vendor and have it custom made for your application.
Lenny at Ultimate has xlnt customer service and does great work.
http://www.ultimateconverter.com
Click to expand...

70aarcuda said:
Got 4 904 racing and they are basically done this way....I use Transbrakes from Tranzact of Indy....

Some had low gear sets in them...some did not....depends on car combo.....a small engine heavy car will want the low gear set....or if you can not run alot of gear in the rear..the low gear set can make up for that somewhat.....

The 71 Dart 360 in my signature is bascially making 500 hp based on its weight and performance...and it has a 904 with 5 stock clutch disc in a 4 disc front drum......you dont need aluminum drums...the 904 is not prone to exploding like a 727 due to the smaller mass of the drum....the 904 sprag is riveted into the case not pressed in as the 727...so you dont need a bolt in spraq....you can change out the roller and springs for 5 bucks....
Click to expand...


These two post are spot on, I do my transmissions the same way.

Billet drum in a 904 is a waste of $500+. If you can twist it 9K+ RPM then you may have an issue. I don't see many SB mopars running 10's turning that RPM.
 
IMO - not a waste - just different strokes...
The reason I'd do it is not only to remove any possibility of explosion - I still feel they are possible and nobody's personal history will change that. My main reason to change it in this application is it replaces the single wound return spring in the high gear clutch with the multiple springs like the 727 has. The other spring can unwind at higher rpm and lose tension leading to issues with the high gear clutch. It also has a larger piston so it holds better. Again - just my opinion. 904s were never meant to be the racing workhorse which is surprising because they are so good at it... I'd rather upgrade once and forget about it.
 
That's unwinding spring is what a 24 spring kit solves for ~100

Testing has shown the 904 drum detonates at ~22-24K rpm... good luck getting there!

In my 40 years being around this stuff and Tony as well... zero 904 explosions and I've yet to meet a trans builder that's seen one either. 727... PLENTY!
 
Mad Dart said:
What you will find out is when you go to get the parts, no single vendor will have them all. I would also say stay away from the BIG name brand guys because they will for sure take all your $$ for the exact same thing you can get down the street for a lot less.

This should be plenty of info on where to get the parts and at least get you started.

Pump Gears** $36
http://www.tcsproducts.com/products/product/13/

24 Spring* $105
http://www.tcsproducts.com/products/product/15/

Billet Strut* $19
http://www.tcsproducts.com/products/product/618/

Rear Kevlar Band* $18
http://www.oregonperformancetransmi...OD&Category_Code=904&Product_Code=PTB-12820AK

Kevlar front Band $19
http://www.oregonperformancetransmi...D&Category_Code=904&Product_Code=PTB-12905F-K

Servo** $17
http://www.oregonperformancetransmi...ROD&Category_Code=904&Product_Code=SNX-22912A

Makco 904 page.* thin clutches/steels & Kits
http://www.makcotransmissionparts.com/A904.html

WIT trans, teflon seals, trans exploded view
https://www.wittrans.com/search.aspx?SearchTerm=12175ct
https://www.wittrans.com/Schematic.aspx?Transmission=A904
Click to expand...

Thanks for posting these links, nice to have it all in one list. :thumblef:
 
Thanks guys good to get the info on this.
I really appreciate the info helps from doing it twice.
I bought a new race car, for those that followed my engine build.
Its coming out of my red car and into the new one.:burnout:
Thats why i'm doing the 904.
Oldkimmer needs to get his car to race track as well.
We aren't getting younger.

Still the converter -which one to buy. TCS or Coan
Valve body -Grinner or Turbo action.
 
Factory Tool for reference....found it on ebay years ago...
 

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good thread just about ready to start i have a 76 904 but not sure what # the trans is but it was in a pickup and backed up a 360 hope it does what i need it to i dont race it on tracks much but sure love to abuse it , i have 2/ 727s for sale if some 1 needs 1 pm me
thanks all
 
winstoninwisc said:
good thread just about ready to start i have a 76 904 but not sure what # the trans is but it was in a pickup and backed up a 360 hope it does what i need it to i dont race it on tracks much but sure love to abuse it , i have 2/ 727s for sale if some 1 needs 1 pm me
thanks all
Click to expand...

Great starting point,the '76 and later 904's had the steel planetary gear carriers which were a weak point on the earlier transes.
 
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