904 race builds

[Ceedawg]

Needing all input on what to do to trans. From roller bearings to clutch discs. What works for you. 340 running high 10s to 11.0

 

[SRT_DSTRHOLC]

CRT Racing has the goods

 

[rmchrgr]

You probably don't need roller stuff for that ET. What year is the trans? A late '70s-early '80s lockup unit is probably not where you want to start because the lockup parts are different than the non. You can try to piece together a "999" but the specific parts that make one up are hard to find. There were only three instances of them before the 904s became lockups.

For parts, I use A&A in Indiana. They have everything you need including "race-prepped" cases which are nice. Basically you'll want 5-6 front clutch discs, (depending on what drums you have) a billet spring retainer thing, billet accumulator, 4.2 lever, the good wide bands and a manual valve body.

For more staring line ratio you can look into a low gear planetary set but make sure you get the sun shell and all the washers and hardware that go with it.

There's really not much to them, just use good parts and it should be fine. They are generally worth .100" in the 1/4 mile vs. a 727.

 

[ch1ll]

Replacement the stamped steel drum with a bullet drum. When things blow, I've read that's usually the cause. Don't forget a trans shield and blanket, safety first. You can't race with no feet real well.

 

[Mopar Sam]

Replacement the stamped steel drum with a bullet drum. When things blow, I've read that's usually the cause. Don't forget a trans shield and blanket, safety first. You can't race with no feet real well.

That is not nearly as bad as a 727 is. I have never heard of a 904 drum exploding, but I am sure it could happen.

 

[Ceedawg]

You probably don't need roller stuff for that ET. What year is the trans? A late '70s-early '80s lockup unit is probably not where you want to start because the lockup parts are different than the non. You can try to piece together a "999" but the specific parts that make one up are hard to find. There were only three instances of them before the 904s became lockups.

For parts, I use A&A in Indiana. They have everything you need including "race-prepped" cases which are nice. Basically you'll want 5-6 front clutch discs, (depending on what drums you have) a billet spring retainer thing, billet accumulator, 4.2 lever, the good wide bands and a manual valve body.

For more staring line ratio you can look into a low gear planetary set but make sure you get the sun shell and all the washers and hardware that go with it.

There's really not much to them, just use good parts and it should be fine. They are generally worth .100" in the 1/4 mile vs. a 727.

Thanks, I’m using a later case that has the larger servo, the steel planets and parts out of the lock up, regular pump housing-input. TA Vbody. Deep pan. I have 2 more trans that I’ll check for the 5 clutch drum. If not I’ll use the good 4 plate one. I’ll have to send vert off to get the hub changed over to flats (hub is cracked) not sure where I’ll send it to, it’s a Lupo 8”. I have a trans buddy I taught to do trans work (his company now) that’s getting me the little parts I need (Reverse wound spring)

 

[Mopar Sam]

For parts, I use A&A in Indiana. They have everything you need including "race-prepped" cases which are nice. Basically you'll want 5-6 front clutch discs, (depending on what drums you have) a billet spring retainer thing, billet accumulator, 4.2 lever, the good wide bands and a manual valve body.

I have had good experiences with A&A.

The other guy was arrogant in person, and in an email with me. He will not ever get any of my money.

I met Rick Allison from A&A at the Indy swap meet years ago, he took time to explain some things to me. No arrogance at all.

 

[ValiantRacing]

Parts from A&A in my 904s, they have some nice upgrades.

 

[rmchrgr]

Thanks, I’m using a later case that has the larger servo, the steel planets and parts out of the lock up, regular pump housing-input. TA Vbody. Deep pan. I have 2 more trans that I’ll check for the 5 clutch drum. If not I’ll use the good 4 plate one. I’ll have to send vert off to get the hub changed over to flats (hub is cracked) not sure where I’ll send it to, it’s a Lupo 8”. I have a trans buddy I taught to do trans work (his company now) that’s getting me the little parts I need (Reverse wound spring)

Sounds like you have it covered. I don’t know what is available out there in terms of billet or lightweight parts but those would be something to look into. A&A will have roller bearings.

5 clutch drums are generally found in A999s so you’ll have to find those.

 

[rmchrgr]

Just to follow up on a few things. As I mentioned above, the wide 5 clutch drums can only be found in an A999 (both lockup or non). The A998 has a 4 clutch drum but I wouldn't bother finding one.

A little over ten years ago I wrote up an 'article' for lack of a better term on how to identify the internal parts of an A999. Since you are starting with a later unit you might want to look through it and verify what you have will work with non-lockup parts which sounds like what you're trying to do.

How to ID a non-lockup A999 transmission with pics

The Moparts thread below is older than mine but it's where I got some of the information from for my thread. There is very specific info in it about what parts you need to make the non-lockup 5 clutch drum work. If you don't get much from my article you should definitely read this one carefully.
https://board.moparts.org/ubbthreads/ubbthreads.php/topics/24397.html
Everything you never wanted to know about 904s

I mentioned it already but I do recommend the A&A race case. It's modified for several things the factory units don't have - first is a rear external vent. I use one of the plastic mushroom looking ones from brand x applications but you could also get an npt-to-AN adapter and run a puke line to a catch can or something. The rear vent is a tight fit to the floor pan so you my have to create a clearance dimple above it to prevent smashing it like I did. And be aware that when you relocate the vent to the rear of the case you have to plug the one in the front of the pump.

The race case is also welded and drilled just above the driver's side rail for an external pressure adjustment port (so you don't have to remove the pan). There are ports for temp and pressure gauges on the other side. There is a cutout at the bottom of the bell for easier converter bolt access. It's a nice upgrade for under $300.

I built my trans around the same time as I wrote the article. A&A sold me 6 thin clutch discs for the forward drum and I think 5 for the rear. Other than the other internal parts I mentioned already, it's nothing special. When I finished it I took to a shop that had a transmission dyno. They ran it and got it to shift and they said it was good to go. Unfortunately I never had it in my car because it's been apart since then but I can't wait to eventually run it through it's paces.

Only thing I've changed since then is the pan. I went with a Moroso fabricated pan because it has provisions for a temp sensor. The temp data gets fed into my EFI ecu which turns on the trans cooler fan at a given temp. It's also way lighter than the cast Summit one I had before.

 

[Ceedawg]

Just to follow up on a few things. As I mentioned above, the wide 5 clutch drums can only be found in an A999 (both lockup or non). The A998 has a 4 clutch drum but I wouldn't bother finding one.

A little over ten years ago I wrote up an 'article' for lack of a better term on how to identify the internal parts of an A999. Since you are starting with a later unit you might want to look through it and verify what you have will work with non-lockup parts which sounds like what you're trying to do.

How to ID a non-lockup A999 transmission with pics

The Moparts thread below is older than mine but it's where I got some of the information from for my thread. There is very specific info in it about what parts you need to make the non-lockup 5 clutch drum work. If you don't get much from my article you should definitely read this one carefully.
https://board.moparts.org/ubbthreads/ubbthreads.php/topics/24397.html
Everything you never wanted to know about 904s

I mentioned it already but I do recommend the A&A race case. It's modified for several things the factory units don't have - first is a rear external vent. I use one of the plastic mushroom looking ones from brand x applications but you could also get an npt-to-AN adapter and run a puke line to a catch can or something. The rear vent is a tight fit to the floor pan so you my have to create a clearance dimple above it to prevent smashing it like I did. And be aware that when you relocate the vent to the rear of the case you have to plug the one in the front of the pump.

The race case is also welded and drilled just above the driver's side rail for an external pressure adjustment port (so you don't have to remove the pan). There are ports for temp and pressure gauges on the other side. There is a cutout at the bottom of the bell for easier converter bolt access. It's a nice upgrade for under $300.

I built my trans around the same time as I wrote the article. A&A sold me 6 thin clutch discs for the forward drum and I think 5 for the rear. Other than the other internal parts I mentioned already, it's nothing special. When I finished it I took to a shop that had a transmission dyno. They ran it and got it to shift and they said it was good to go. Unfortunately I never had it in my car because it's been apart since then but I can't wait to eventually run it through it's paces.

Only thing I've changed since then is the pan. I went with a Moroso fabricated pan because it has provisions for a temp sensor. The temp data gets fed into my EFI ecu which turns on the trans cooler fan at a given temp. It's also way lighter than the cast Summit one I had before.

Great info, I’m glad someone like you went to the trouble of getting the facts straight. I’ll use the guts from input back from the lock up trans making sure the reg input and hub fit properly. I’m thinking the wound spring could be less pressure to help hold that front clutch better, only time it’s NOT applied is park and reverse. I had a Clutch Flight trans back in the 70s, the front clutch plates were drilled and bolted, no back up, it was made for those fuel altered cars.
Did you raise line pressure on your trans? I was always a 727 guy these 904 are new to me, mainly because always raced big blocks and Hemis.

Laying in bed at 5 in the morning thinking of this trans..
My bad on the spring in front clutch, I confuse myself over thinking to much lol. It’s the rear clutch that stays engaged except for reverse. I need to step back for awhile and process this better (getting old) the main reason I’m asking you guys this stuff.

 

[Ozyduster]

Great info, I’m glad someone like you went to the trouble of getting the facts straight. I’ll use the guts from input back from the lock up trans making sure the reg input and hub fit properly. I’m thinking the wound spring could be less pressure to help hold that front clutch better, only time it’s NOT applied is park and reverse. I had a Clutch Flight trans back in the 70s, the front clutch plates were drilled and bolted, no back up, it was made for those fuel altered cars.
Did you raise line pressure on your trans? I was always a 727 guy these 904 are new to me, mainly because always raced big blocks and Hemis.

are you going full manual? The kickdown is what normally hurts boxes especially when not done right. Have a few mates with 600+hp and even with kickdowns installed they will never use it. Think ill go full manual on my 904 as looking at 600hp hemi

 

[65TerrorCuda]

Just to follow up on a few things. As I mentioned above, the wide 5 clutch drums can only be found in an A999 (both lockup or non). The A998 has a 4 clutch drum but I wouldn't bother finding one.

A little over ten years ago I wrote up an 'article' for lack of a better term on how to identify the internal parts of an A999. Since you are starting with a later unit you might want to look through it and verify what you have will work with non-lockup parts which sounds like what you're trying to do.

How to ID a non-lockup A999 transmission with pics

The Moparts thread below is older than mine but it's where I got some of the information from for my thread. There is very specific info in it about what parts you need to make the non-lockup 5 clutch drum work. If you don't get much from my article you should definitely read this one carefully.
https://board.moparts.org/ubbthreads/ubbthreads.php/topics/24397.html
Everything you never wanted to know about 904s

I mentioned it already but I do recommend the A&A race case. It's modified for several things the factory units don't have - first is a rear external vent. I use one of the plastic mushroom looking ones from brand x applications but you could also get an npt-to-AN adapter and run a puke line to a catch can or something. The rear vent is a tight fit to the floor pan so you my have to create a clearance dimple above it to prevent smashing it like I did. And be aware that when you relocate the vent to the rear of the case you have to plug the one in the front of the pump.

The race case is also welded and drilled just above the driver's side rail for an external pressure adjustment port (so you don't have to remove the pan). There are ports for temp and pressure gauges on the other side. There is a cutout at the bottom of the bell for easier converter bolt access. It's a nice upgrade for under $300.

I built my trans around the same time as I wrote the article. A&A sold me 6 thin clutch discs for the forward drum and I think 5 for the rear. Other than the other internal parts I mentioned already, it's nothing special. When I finished it I took to a shop that had a transmission dyno. They ran it and got it to shift and they said it was good to go. Unfortunately I never had it in my car because it's been apart since then but I can't wait to eventually run it through it's paces.

Only thing I've changed since then is the pan. I went with a Moroso fabricated pan because it has provisions for a temp sensor. The temp data gets fed into my EFI ecu which turns on the trans cooler fan at a given temp. It's also way lighter than the cast Summit one I had before.

Do they drill the oil feed for the sprag? I'm planning on doing that to mine since it's on the bench. I thought I was done but then I saw the Cope video on it.

 

[crackedback]

904 race tranny Recipe

I think there may be a reverse wound spring to replace one of the more expensive items.

 

[rmchrgr]

Did you raise line pressure on your trans?

I have an older T/A FMVB #17675 which they don't make anymore. Ten years ago when I built my transmission, I talked to Paul about it and he said pressure will be 130psi. Don't quote me on this but a RMVB should create more pressure, like 140psi +.

Again, I have not run it since I built it but once it's in the car I can experiment with it since it's easy to do. From a S.O.T.P. perspective, my old 904 that was built very similarly using the same valve body shifted HARD.

Do they drill the oil feed for the sprag? I'm planning on doing that to mine since it's on the bench. I thought I was done but then I saw the Cope video on it.

If you are referring to the race case from A&A, I'm not sure. They don't list that modification specifically in their description. I'm sure they could do it if you asked. I didn't watch any video but my guess is it's probably not necessary for most applications. Also, if he was talking about it for a 727 that idea may not apply to a 904 the same way.

I provided the link to the A&A case in post #10 but here is the copy:

"These cases are machined to allow pressure adjustments while still in the car. They have a cut-out in the bell housing for easier converter bolt access. Lubrication and venting has been improved. Each case is glass beaded, bores are honed, bolt holes are tapped and looks brand new."

I looked around to see what kind of blingy parts for 904s are available, click the links below;

TCS offers a billet front drum and an aluminum pressure plate kit.

A&A also has billet aluminum drum stuff, roller parts and lightened sun shells.

Far as I can tell from their website, CRT does not seem to list much in the way of 904-specific parts. I imagine they could suggest and obtain whatever you want though.

The ultimate unit would probably be a Pro Flite but those are $6-7K+.

 

[65TerrorCuda]

I have an older T/A FMVB #17675 which they don't make anymore. Ten years ago when I built my transmission, I talked to Paul about it and he said pressure will be 130psi. Don't quote me on this but a RMVB should create more pressure, like 140psi +.

Again, I have not run it since I built it but once it's in the car I can experiment with it since it's easy to do. From a S.O.T.P. perspective, my old 904 that was built very similarly using the same valve body shifted HARD.


If you are referring to the race case from A&A, I'm not sure. They don't list that modification specifically in their description. I'm sure they could do it if you asked. I didn't watch any video but my guess is it's probably not necessary for most applications. Also, if he was talking about it for a 727 that idea may not apply to a 904 the same way.

I provided the link to the A&A case in post #10 but here is the copy:

"These cases are machined to allow pressure adjustments while still in the car. They have a cut-out in the bell housing for easier converter bolt access. Lubrication and venting has been improved. Each case is glass beaded, bores are honed, bolt holes are tapped and looks brand new."

I looked around to see what kind of blingy parts for 904s are available, click the links below;

TCS offers a billet front drum and an aluminum pressure plate kit.

A&A also has billet aluminum drum stuff, roller parts and lightened sun shells.

Far as I can tell from their website, CRT does not seem to list much in the way of 904-specific parts. I imagine they could suggest and obtain whatever you want though.

The ultimate unit would probably be a Pro Flite but those are $6-7K+.

Here's the video, Cope does it to all his trans both 904 and 727, I can attest to the wear because my case looks just like his. This was the source of aluminum dust in my pan. Will it fix it? Time will tell.

https://youtu.be/T9q318sedx8?si=M8YHP4mNHD9Rclv0&t=188

 

[rmchrgr]

I don't have a bolt-in sprag. I didn't watch the whole video but I saw the oil hole part.

The factory didn't feed constant oil to that area for the OE press-in clutch. Perhaps because it was press-in style there was no need?

The volume of oil going through that extra hole is probably not too significant but it could bleed off a little pressure in the cooling circuit. What that means, I don't know either but everything you do has another side to it.

 

[9secRR]

904 in my car. They can take a lot of power if built properly.

I will try to find the parts list. It was built 10 years ago.

 

[Ceedawg]

Update on what I have, 78 case, steel planets and their parts, 4 drum with the five thin plates, flat type pump, TA forward pattern VB, deep pan. Dynamic 4500 Converter hub is being changed to the flats type.

 

[mshred]

Update on what I have, 78 case, steel planets and their parts, 4 drum with the five thin plates, flat type pump, TA forward pattern VB, deep pan. Dynamic 4500 Converter hub is being changed to the flats type.

Sounds good to me! I ran 9.70's with nitrous and lots of street miles in a 3400lb car with a 904 that had pretty much what you described, but I never changed the pump lug style. You don't need shafts, cases, bolt in sprags, or a billet drum with what you are doing. The diameter of the front drum in the 904 requires a lot more for it to do the 727 grand kaboom...but a blanket doesn't hurt if you are still somewhat concerned.

Just my experience.

 

[rmchrgr]

Update on what I have, 78 case, steel planets and their parts, 4 drum with the five thin plates, flat type pump, TA forward pattern VB, deep pan. Dynamic 4500 Converter hub is being changed to the flats type.

Having 6 clutches in a 904 is the most desirable setup but 5 will obviously hold better than 4.

Just out of curiosity, what is the PK number on the pan rail of your unit? For reference, I've attached a PDF of the trans guide that's been on the internet forever. It lists unit PK numbers from 1965-1986.

If anyone cares - almost exactly ten years ago I detailed the assembly of the 904 that's in my Duster. Click this link and go to post 182.

 

[Ceedawg]

Sounds good to me! I ran 9.70's with nitrous and lots of street miles in a 3400lb car with a 904 that had pretty much what you described, but I never changed the pump lug style. You don't need shafts, cases, bolt in sprags, or a billet drum with what you are doing. The diameter of the front drum in the 904 requires a lot more for it to do the 727 grand kaboom...but a blanket doesn't hurt if you are still somewhat concerned.

Just my experience.

I might have to run some type of shield, rules, anything faster than 11.00

 

[Ceedawg]

Having 6 clutches in a 904 is the most desirable setup but 5 will obviously hold better than 4.

Just out of curiosity, what is the PK number on the pan rail of your unit? For reference, I've attached a PDF of the trans guide that's been on the internet forever. It lists unit PK numbers from 1965-1986.

If anyone cares - almost exactly ten years ago I detailed the assembly of the 904 that's in my Duster. Click this link and go to post 182.

I got those numbers and I’ll look later today.

 

[Ceedawg]

Having 6 clutches in a 904 is the most desirable setup but 5 will obviously hold better than 4.

Just out of curiosity, what is the PK number on the pan rail of your unit? For reference, I've attached a PDF of the trans guide that's been on the internet forever. It lists unit PK numbers from 1965-1986.

If anyone cares - almost exactly ten years ago I detailed the assembly of the 904 that's in my Duster. Click this link and go to post 182.

Early trans, 72 I think after seeing the date. People don’t always tell the truth.

 

[ValiantRacing]

I know 71 and later, A&A offers billet servos for both.