I've decided i'm going to make the switch in my valiant from 727 to 904 in hopes of picking up the .15-.2 everyone says a 904 will net you.

So anyhow, i gathered up some local 904s and need some advice on what's the best plan of attack as far as parts to use and upgrades needed to survive my low 10 second 3000# car running a transbrake.

I've got a 73 and a 74 904, and an 86 999 transmission. I'd really like to be able to use the 5 clutch high gear drum from the 999, but am planning on holding off on using the low gear set. I'd like to see the back to back difference of standard gear 904 vs 727. Maybe later the low gear set will sneak it's way into the transmission.

What is the best case to build this transmission from? What changes are needed to run the 999 drum? Necessary modifications to the transmission to make it live? And finally, what's a good rebuild kit to use for it? thanks for listening! Andy

Would it not be less expensive to upgrade the engine than the trans?
What are the engine specs?

Run this for sure.

http://www.tcsproducts.com/details.html?id=15

i'm running a, i think it's a 1971 904. 440 sb, 9.69@138.50. according to a&a, drum isn't a problem. billet low rev servo, red alto plates, harden strut, use teflon seal rings on support. line pressure is critical. should hold up with 180#, since 904 plates have a smaller surface area than a 727. i have a low 1st gear, 60'-1.30. stay safe, seeya.

You most likley would want a later case(lock-up) as it has a slightly better sprag.(Mine are both earlier)I would always use a rollerized ouput shaft support w modified shaft.I move the vent to the tail shaft. I like a double wrap rear band.I've rollerized my rotating assembly but it doesnt pick you up much.I always use as many rear clutches as I can get,I think 4 is all you can get in one.The pump and front drum are the tricky area to get the right parts as you cant use any lock up pieces as your front drum wont seal right. I like the widest front band I can get to fit right. I also like the scarf cut sealing rings.Also I use the multi spring pack in the front drum.The sealing rings and spring pack are from A&A.I really like the 2.74 1st gear. My car leaves hard w/ 1.27 60'.There was several posts in the archives that might help w/ proper part selection.Thats all I remember off the top of my head.I've probobly left out a few things.

Look up Dizusters archive post on swapping the front drum/pump parts. Do it wrong and you'll be chasing your tail with high gear clutch failures. It took forever to figure it out. We asked EVERYONE.
Doug

I'm not saying the combination on the motor is perfect, but I doubt there's anything I can do to pick up .2 for the price of builiding a 904.

408 bottom end, steel k1 crank, k1 rods, diamond flat top pistons, factory block
Indy 360-2 cnc heads, Indy intake converted to dominator flange.
1050 dominator
262,268@ .050 solid roller. .698 lift
10.3:1 compression. Pump gas motor

3000# race weight valiant
4.56 gear, 29.5x10.5 slick, ladder bar car
727 with transbrake, 5400 converter

The only thing I think that would pick the car up would be to increase compression to 11-11.5 compression. However, with the Indy moved exhaust valve, there is no radial clearance on the exhaust valve relief...

I also replace all the bushings and thrust washers, multi spring retainer as shown before, and I buy my kit's from Mancini, MRE 006 has the blue plates and kolene steel also a kevlar intermediate band (don't use it with a aluminum drum)use the 999 high gear drun and you will have to have the back of the pump machined for clearance, reenforced band strut and do the oiling mod's that I believe are in the tech section or the archives,, and also keep the line pressure up if you use the TA valve body it has only about 125# of line pressure, need to get that up around 150# or a little more, A@A has a spring you can replace on the VB that will up the pressure and greatly improve the action of the VB and clamps the clutches harder.

Anyone have a link to these oiling mods? I'm having trouble finding them. Thanks- Andy

Just use an early trans, so you don't have to deal with the lock up stuff which HP parts are limitied.

You don't need the bigger drum from the 999. You can buy thinner discs and run 5 in the 904 drum. You will also need a shim kit to get proper clearance. And mixing parts is a PITA. Don't deal with that headache.

Put good bands, clutches, and steels in. Get a Valve body from A&A, rebuild the trans, put in a blocker rod and put in a billet piston and 4.2 lever.

I have nothing else done to my trans and I'm running it with a 7100 stall. 878 hp 563 tq...

No trans brake though, so Rick may be able to recommend what else you HAVE to do.

I have less than $800 in my trans besides the trick custom valve body Rick built me. I have 37 1/8 mile passes and 52 street miles on it. No issues and the oil pan shows no problems...

Just my

It has been a loooong while since I have done any 904 work .... but try and find some of the green metallic waffle Raybestos front clutches. NEVER seen a failure with those pieces.

Everything that needs to be said has already been said but I don't think you'll see 2 tenths, especially without the low gear. I think you'll be lucky to see .08.

904 is 27 lbs lighter with 17 lbs of it rotating. Call Rick Allison at A&A.

4.56 gear and 29.5" tire?! Woohoo!

Its funny all of the guys running 904's in fast big cube small blocks. I just blew the crap out of mine and was considering going to the 727 with the kind of HP my stroker W2 is making...But it looks like you guys have made them work, so maybe I will rebuild the 904 I have and get the convertor freshened.

Big HP 904 I would run a 5.0 lever, but a 4.2 is the next best thing. 904's need the clamping force. 904's will break input shafts from time to time, but I would only worry about it when you actually break one.

The best core to get is the 1975-1977 360 904 trans, which is a non-lock-up, wide 5 clutch front drum, and steel planets. You can upgrade to the 2.74 low gear set which are found in 1981-up 904's. This will allow a better launch without increasing the rear axle ratio. I would use Red lined bands that are solid backed, NOT flex bands. I have had good luck with the standard Raybestos Tan waffle clutches for high gear, with an upgrade to the Alto Red Eagles, www.altousa.com . Use the 2 spring front servo with at least a 4.2 lever. Use the 5.0 lever if you are really pushing a high pressure valvebody or using Nitrous. The 4.2 should work with most applications. Use a bronze output shaft thrust washer between the front of the output shaft and the rear of the forward clutch retainer. Set all end plays to minimum factory specs. Set direct clutch clearances to 0.010"-0.015" per disc or to the valvebody manufacturers' specs. The forward clutch clearance to 0.020" - 0.035", and use only FLAT selective snap rings. I would use the Griner 1222G20B transbrake w/ low band apply.

You can install a shim in the low/rev servo piston to allow a better 1-2 shift. Most valvebodies have all these extras to aid the VB to better performance. I use the MP deep pan with drain plug and a good cooler. I also use Turbo Action converters with excellent results. I currently use a '73 core, 2.74 low, wide 5 clutch drum, T/A Cheetah valvebody, T/A 8" converter, deep pan, T/A Tranz Box rebuild kit. Rick Allison at A&A www.aandtrans.com is top notch and can provide any parts you need, and John Cope at CRT sells A&A parts as well.


I would recommend 5 direct clutches no matter which drum you have. Use A&A thin direct clutches, P/N 12750A-6 if you have the standard 4 clutch drum. This will allow 5 clutches in the 4 clutch drum. If you have the wide 5 clutch drum, just use 5 Raybestos Tan waffle clutches. Also, concerning the front band, I would use the narrow center apply lug solid red band (kickdown, with grooves) on either the standard 4 clutch drum OR the wide 5 clutch drum. Normally, the wide drum gets a wider band, however, the apply lug on the band is offset from the center, and thus does not apply the band evenly, causing uneven wear, overheating, etc.

In order to use the wide 5 clutch direct drum, you need a forward drum with input shaft from a non-lock-up trans. These will have an 1-1/8" wide splined clutch hub that fits into the direct clutches. The clutch hub for the standard 4 clutch direct drum has a 1" splined clutch hub on the front end of the clutch retainer. Also, you need a beveled back front pump reaction shaft support to clear the wider 5 clutch drum. You need to keep the years separated when swapping parts, 1975-77 or 1978+ all non-lock-up. The diameter of the sealing rings on the input shaft have a 0.062" difference between the two year groups and do not interchange.

www.aandatrans.com

www.coperacingtrans.com

www.tcsproducts.com

www.727specialist.com

The 904 clutches have about 1/2 the surface area of a 727, so in order to live behind some serious torque, more line pressure is needed.

904 FLAT snap rings for clutch drums: (Mopar P/N's)

1942421 0.060"

1942423 0.076"

2538617 0.098"

These numbers are old, and may be superceded to newer P/Ns. Ask your local Mopar dealer to check availability and price. If they don't have a way to order them, ask Rick at A&A, as he sells a kit with them. One required for each drum (2), and of the correct thickness to set clutch clearances properly depending upon which drum you are adjusting. In some cases, the snap ring will not give you the exact clearance you need. It is better to go a little loose than too tight. Also, A&A sells different thickness steel plates that fit between the clutch discs to help in zeroing in on the correct clearance. Another option is to machine the thick outer pressure plate a little if you have to. A machine shop should be able to grind the plate like a flywheel for a good flat surface after you figure how much needs to be removed. Remember, measure as many times as needed to be sure, and cut once.

For reference, the snap rings that hold the gear train on the output shaft are selective, and are used to set gear train end play. These are the Mopar P/Ns:

06026289 0.041"

06030938 0.062"

06030404 0.084"

Remember, always set the gear train end play and the input shaft end play close to minimum factory specs. The input shaft end play is adjusted by using a selective thickness fiber washer between the front pump and the direct drum. I don't have those numbers handy, but Rick would be able to help you with those as well.


I mostly buy parts separately. I can buy a standard rebuild kit locally with Raybestos clutches, and I simply buy the performance solid red bands from A&A, CRT. They usually require a core to return as the solid bands are getting scarce. However, you can buy a complete race kit from either CRT or A&A. They can build to kit the way you want it. I have also bought from Bulk parts at a real good price,

http://www.bulkpart.com

At your power level and weight, you may need 300M steel input and output shafts. I would ask Rick Allison at A&A for his recommendation. Roller thrust bearings with steel planetaries may also be needed to ensure longevity. Aluminum direct drum may not be necessary in a 904 due to the smaller diameter and lower inertia, there is less probability of explosion.

Main parts needed are a well designed high pressure transbrake to keep the small clutches and bands from slipping, good quality clutches and solid backed bands, pay attention to detail with clutch clearances and gear train & end play dimensions, and a rear roller support with oiling mods to the sprague and direct clutch oil port in the reaction shaft support. A multi-spring pack for the direct clutch to replace the single coil spring.

John

Your the man!