What is the story on the trans picture then? Everybody I've ever heard talk about it said neutral drop.

That driver never used a neutral drop. It was a used case that had the ORC cam loosen up, it walked forward but not uniformly. (That’s the purpose of the set screw - to keep the cam tight. The splines are there to keep the cam from turning).

Once that happens the rollers are no longer perpendicular to the axis of the race.

Lots of testing in later years showed what it took to fail the ORC, you can see the efforts of those tests in all the changes made to the ORC, both in the 727 and 904 family of transmissions.

Shy of the cam getting torn loose from the case, the vast majority of failures show roller misalignment - that’s from roller spit back.

Not my opinion, results of testing and post mortem tear downs on hundreds if not thousands of transmissions from field returns and race units too.

I’m not saying to not use the good drums - sometimes it depends on the driver and sometimes the circumstances.
I advocate using the drum too.

ORC?

Overrunning clutch - or oneway roller clutch.

Chrysler never used a “sprag” clutch in 727 or 904.

Sprays use dog bone elements, ORC uses rollers with a cam.

IIRC, the neutral drop car was a '67 Hemi that sprayed oil on Buster Couch.

Whatever happened to the steel jacketed alum drum ??

that's what I have in my transmission, nice piece, been in there over 5 years, TCS makes them.

The picture of my friends car started with breaking the rear gear on launch, shocked the driveline, the rest was a huge learning experience. Chuck Lofgren was at the track that day and came by to inspect.... and gave us a valuable lesson on what happened.

Years later the same thing happened to my cousins car at MaTS... drum didn’t explode, but broke the gear on launch and hit the trans so hard it broke the case and split the ring holding the rollers.

That's the story that I know of, Jack Werst aka Mr. 5/50 launched the 67 Plymouth using a neutral drop and sprayed the starting line guy with hot transmission fluid.

The story goes that after that happened Neutral drops on the starting line were banned.

It's strictly a product of engine RPM. If the engine is capable of achieving 5000+ RPM in Neutral then it has the potential to grenade the drum if the overrunning clutch fails.

Kevin

Happy Christmas Transman and all Mopartians!

Bolt in Sprags are what modern folks call ORC's...
Don't matter what its called as long as you got one lol...

Not really a newbie, as I've been racing Mopars since the 80's...
The info I get is from Mopar sites so its only as good as the posting-peeps, who put the info up, for Dorks like me...

Neutral drop 'was a thing' but its banned now, so the info is very old and pre computers and sensible people.

When I think of the 'use and abuse' we gave almost stock transmissions, IT MAKES ME BLUSH!
We all know better now and even the old experts can make mistakes, I lost a prop once by not fitting the C-clips.
They were never there to start with and it lasted for years without anyone noticing, the damage was outrageous...

But nothing compared to the damage done by an exploding drum...

All I'm saying is, if you are a drag racer, even in a 15 second car, YOU NEED A BILLET DRUM...

Don't be a DINOSAUR and think its gonna be OK...

ASK Brokenfoot

we used to do "J hooks", go fast in reverse, then while holding the pedal down, slam into 1st. it's amazing we never "broke" anything !
sure made neat marks on the street though. you were really good if you could do curlycues doing that.

I saw a girl at ubly dragway in a 14 second car do the exact same thing she broke her foot also.

Buddy of mine used to steal his Gramma's 71 Fury 318/904 and go hellraising. He used to floor it in reverse and get the tire smoking, then leave it floored and slam it back and forth between drive and reverse. He would actually cut a trench in a blacktop road. I have no idea how he never shelled the u-joints or anything.

That procedure was actually part of what they called a “rock test” at Chrysler Chelsea Proving Grounds.

I don’t recall if it was at a WOT or just a high rpm. It was done to simulate getting stuck in snow, etc. I believe it had to handle 50 cycles of reverse to drive to reverse.

hi

if you all were old enough to rember there was a mopar <plymouth > comercial on tv with a guy talking about mopars with a 69 ply fury in the back ground tires smokin goin forward / reverse the whole time !

Oh well, what can one say about stuff like that?

So everyone thought the ORC's were indestructible and would never fail...
I can't believe that you could get away with the stuff you talk about on here?

I've seen drum explosions here and in the USofA and they still happen.
That's me put firmly in my place methinks...

Well, as in much of what we use in racing, we inherited a certain design that was never intended to be abused like they are or see the power levels they are used at or
re-used for 50 + years.
The rock cycle test was part of a D-FMEA - and the test was to simulate someone placing the trans into gear with the choke on, high idle and also to simulate being stuck in snow or whatever. And that test was to make sure the ORC cam remained in place, the cam was hard enough, the L/R drum was robust enough, and the race strong enough.

What was found later was that certain events caused ORC failure, for example shifter in drive, take off deep throttle and lose and gain traction like driving from a dry spot to wet and back to dry spot. Or in a burnout. It caused roller spitback. That’s where the sprag is better suited since you can’t upset the links.


Anyways, have a Merry Christmas. And here is to keeping both feet.

john, i wasn't ragging on you in any way, and i apologize if i came off as a [censored].
i will take my beating now..........

i was just saying what we did when i WAS a [censored] back in the day, and i am amazed at what we DID get away with !
today, i just shake my head and wonder why my pals and i aren't croaked or maimed, the stuff we did.

i certainly know better today !
merry Christmas, and i hope i don't offend in the future.

....boy they must have left that test in the past with the 94ish RH trans came along. We repaired so many of those that had gotten stuck. Seems to me most of them welded the output shaft to the OD piston retainer. I was just getting into “the business” at the time and a guy I worked with was losing a check ball and drilling the separator plate. Engaged a bit harsh... but they lived.