Never seen or heard of a stock 904 drum blowing up. However, that doesn't mean that normal precautions like making sure the roller clutch parts are in perfect condition, use of LBAVB where they should be, proper burnout and driving procedures, inspection of the trans after a driveline failure, etc., because they will fail and tear up parts and possibly the case.

~ 50 passes was the norm. When it started to drip a bit of oil on the trailer floor, it would get pulled and sent for repair. Got to be expensive.

Out of curiosity, I pulled a fresh one out with like 5 runs on it, just to look. The crack in the corner had already started. I haven't run one for awhile but the new style hub and pump gear is supposed to have fixed all that.

Anyone can jerk one apart and slap it back together. Getting clearances, end plays, oiling in the back with a manual VB, and all the other details dead nuts is the most important thing. The parts upgrades needed are mostly dictated by horsepower/RPM levels.

Agree on that. No need for a billet drum in a 904. If you want one, run it. Have seen them get distorted over time, never seen on explode like 727's do. Critical mass RPM is likely never seen with any bracket racer SB.

A billet drum or two have failed in 727's. Billet doesn't mean safe, just less likely.

Yep I just jerk em apart, ain’t that the way?

There’s actually an even cheaper alternative available too.... a reverse wound spring.

http://www.atiracing.com/products/trans/904/index.htm

Our 904 hadn’t been used since the mid 90s when my dad was racing the Duster with our iron head 360. Chuck Lofgren built it for him and his attention to detail is second to none. I’m certain he wouldn’t recommend this build for a low 9 goal, but I was just kind of curious. We too suffered a cracked converter drive once, but Dynamic changed the hub and it never happened again. Not wanting to test that converter, and it wasn’t trans brake friendly, I sent it to Lenny as he had data on our build and had it nailed down pretty good, I had him change the drive to the A500/flat style. A&A used to have the gears, but I don’t see them listed anymore.

Nothing personal. Just a general statement.

I just bought some from A&A last year. The A&A page is a little clunky and doesn't sort well off the search feature. But they are great to deal with on the phone so I just call them anymore.

[quote=cudaman1969 Don’t need a pro trans. Thanks [/quote] Does that really mean you don't want to pay for the good parts that Pro Trans uses in their race trannies?
If so you may need them and won't save money by not buying and using them now instead of buying them later
Mopar designed the 904 for low power use in 6 cylinders, 272 and 318 V8, not for high powered cars that would get beat on a lot under warrentty
Dave found out that by using some of those lighter weight parts and beefing them up to work well and live in drag cars was a good way to make those cars go faster without having to make more power with that combination, reduce drag and improve net power
Maybe you should think of buying and using one of his special race built Pro Flytes for your car

Does 500 HP and never going over that warrant a $6000+ trans? My opinion, no. Some people can tear up an anvil. I want an upgrade that will fit MY racing habits not Joe Blows who can’t do a burn out proper and no clue when the sprag is broke.

Just because the car moves, don't assume the roller clutch is OK.

Fellow has a street/strip car, A body with a fairly stout G3 Hemi with a 904. Broke some teeth off the ring gear or something. Fixed that and took the car out for a drive. Seemed ok except for a slight vibration. Check the driveshaft and all that and couldn't figure it out. He was about to say the heck with it and go to the track. I convinced him to pull the trans and bring it to me.

Half the springs in the roller clutch were smashed flat when it freewheeled. Half the rollers were just along for the ride and the other half were actually holding well enough to drive it. It would not have survived the first hit. The vibration was the inner race and reverse drum being forced to one side by the rollers that were still halfway working. Just not worth taking a chance.

Do I know people that have broken 904 input/output shafts running 10’s? Yes. Both were trans brake cars in the 3100lb range. On the flip side I know people who’ve run for years with no probs. Starting to sound like an 8.75 conversation.... only you can get parts to make the 904 live
.

Agree 100%

What I plan on doing to my 904…. I’m going to go billet shafts and I’m going to get it machined for roller bearings. I’m retaining the stock components unless convinced otherwise.

I have a new 904 on order, supposed to ship next week .. I will see how well it holds up

What’s the combo?

Nothing crazy, just a 530 hp small block

That will test it

Will be interesting to see the build sheet on that…. at least I know where a spare is if I need one over Labor Day weekend

Keith has a 904 behind the 499 in MoparJohn's GTX. So far all I know that has broken was an input shaft. Keith found a supplier for hardened ones I believe.