Boom goes the......
- Thread starter inkjunkie
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abodyjoe
Well-Known Member
Those things are ticking time bombs. I'll take a 904 everyday.
TrailBeast
AKA Mopars4us on Youtube
I have never personally seen one that exploded, but I have seen one that cut itself in half because the sun gear shell flared from an overrunning clutch failure.
It probably would have exploded if it was race car, and not just a driver.
It probably would have exploded if it was race car, and not just a driver.
EL5DEMON340
Well-Known Member
Need a bolt in sprag even for a street car
ram45red
Well-Known Member
I always thought a 727 was more heavy duty than a 904. Ran a 727 in my street rods all these years with no problem. I want to build a bracket car and already have two 727s for small blocks.Do I need to reconsider using them?
roccodart440
Well-Known Member
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If the build on that tranny was as good as the rest of the car...
Yep.
Billet drum is the only way to reduce this issue to almost nil. That piece only runs 500-700 alone during a build and is not necessary in a 904 trans.
TrailBeast
AKA Mopars4us on Youtube
You should have a blanket for it at least.
Also, any time there is a driveline, ujoint or rear end failure the trans should be torn down for inspection and replacement of the sprag.
They make a billet replacement front drum that has much less of a chance of exploding.
People have lost feet and legs over this.
ram45red
Well-Known Member
I'll start looking into a billet drum,bolt in sprag and blanket/shield or going with a 904.
I've blown up 4 904 transmissions , all went straight to the junkyard ,cases had massive cracks or chunks missing . MY 727 transmissions all lasted over 300,000 miles one in my Ramcharger with a 600hp 440 that was raced and used off road never had a problem .
Supershafts
Well-Known Member
Thats what happens when you cut corners building it.
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Burntorange70
Well-Known Member
Scary stuff. The floor in my Dart is all scarred up from when the 4 speed came apart. Happened way before I got it so cant say if the driver walked away.
younggun2.0
Well-Known Member
no first gear burnouts!
Inertia
Well-Known Member
I've seen and heard the stories, and am a bit surprised.. Back in the day we were one of the first places to install Mopar's Rev Man shift V/bodies,, and built dozens of 727's running behind hemis and smaller,, The only probs we had was tailshafts breaking occasionally,, and the owner forgetting the reverse pattern,, and shifting into the "old" hi gear (now low gear),, and buzzing the engine,, saw a few engines lost that way..
But our news came once a month via rod mags,, the internet has made all these occasional blow-ups more available...
Back then, and now I suppose,, we all went to the track to try and break our cars,, and when they broke,, we just built them stronger,, hearing about a breakage was just to be expected.. But seldom heard of a 727 or an 8 3/4 failing... jmo
But our news came once a month via rod mags,, the internet has made all these occasional blow-ups more available...
Back then, and now I suppose,, we all went to the track to try and break our cars,, and when they broke,, we just built them stronger,, hearing about a breakage was just to be expected.. But seldom heard of a 727 or an 8 3/4 failing... jmo
transman
Well-Known Member
High mileage cast iron drums will and do explode more often than you think. If you're racing, steel or aluminum drums the only way to go. I once had a sheet that showed at what rpm these drums would explode. If there's enough interest, I'll get the sheet and post it here.
transman
transman
please do .
The 727 is one of the best transmissions made. Period. The problem with transmission explosions is one thing. Operator error. Installing a manual valve body and eliminating doing the burnout in first gear will completely eliminate the problem. No need for a bolt in sprag, although it is a nice addition. The fact is, that if you do the burnout in first gear and shift into second and the tires hook shifting into second the shock will rip even a bolt in sprag out and the transmission will likely still explode. Simply doing the burnout in second gear will all but eliminate the problem.
2 Darts
A-body Addicted
Youch!! I've seen clutches take off through floorboards, but this is the first automatic I've seen pictures of after catastrophic failure. Got my attention now concerning racing an automatic. IMO the driver was fortunate.
Mad Dart
Nothing to see Here!
I got one on the stand for my TT build. It's got a Billet aluminum front drum, bolt in sprag, RMVB, & Transbrake with low band apply along with all the other go fast goodies.
For sure as stated, driver error comes into play.
My 904 I built has dead hooked several times. It's got the same valve body "low band apply" but no brake. The 904 is very strong Trans is all I can say when they are built right. Damn!
For sure as stated, driver error comes into play.
My 904 I built has dead hooked several times. It's got the same valve body "low band apply" but no brake. The 904 is very strong Trans is all I can say when they are built right. Damn!
My engine builder keeps "suggesting" that I build a nice 904 to put behind the 408 that I'm building. I have a rebuilt 727 with a couple thousand miles on it but it has always leaked fluid. Member VOETOM is going to help me tear it apart, check everything out, and put a new set of gaskets and seals in it. This is a street only car but should be pushing 500hp pretty easy and will be doing lots of burn outs. Is a bolt in sprag really necessary for a street car?
With the internet, a couple of transmissions blow up on people's race cars, and all of the sudden people are afraid of a transmission that is in THOUSANDS of hot rods and muscle cars. We used to pound on BB 727's pretty hard back in the day and never had anything explode?
With the internet, a couple of transmissions blow up on people's race cars, and all of the sudden people are afraid of a transmission that is in THOUSANDS of hot rods and muscle cars. We used to pound on BB 727's pretty hard back in the day and never had anything explode?
People will argue with this till they are blue in the face, but a bolt in sprag is not necessary. It will do nothing to keep the explosion from happening. It will simply make the carnage less.
The failure occurs when the front drum RPMs become so great, the outside or the shell flares out and locks against the case. When this happens, it doesn't matter what kinda sprag you have, that transmission IS comin apart.
Since it is harder to spin the bolt in sprag out of the case because it is bolted in, it absorbs more of the shock of the explosion. In other words, it takes more to tear it out of the case......but it WILL tear out.
It's easy to see in any 727 explosion the kinda force that's dealt with. A bolt in sprag will NOT stop it. It will slow it down. I am sure there have been instances where a 727 with a bolt in sprag didn't come completely apart, but in those cases, the explosion was not as violent......probably because the sprag helped hold it together, or the RPMs were not quite as high as other failures.
The reason the transmission fails has NOT ONE THING to do with the sprag. The reason for the failure comes from doing burnouts in first gear and having the tires hook up on the 1-2 shift. The resulting shock is what causes the transmission failure.
A manual valve body will totally eliminate the entire problem IF the operator will simply do the burnouts in 2nd gear. NOTHING else is required. No bolt in sprag, nothing. They are a nice addition, but the only one thing that stops the failure is the manual valve body that allows 2nd gear burnouts.
The failure occurs when the front drum RPMs become so great, the outside or the shell flares out and locks against the case. When this happens, it doesn't matter what kinda sprag you have, that transmission IS comin apart.
Since it is harder to spin the bolt in sprag out of the case because it is bolted in, it absorbs more of the shock of the explosion. In other words, it takes more to tear it out of the case......but it WILL tear out.
It's easy to see in any 727 explosion the kinda force that's dealt with. A bolt in sprag will NOT stop it. It will slow it down. I am sure there have been instances where a 727 with a bolt in sprag didn't come completely apart, but in those cases, the explosion was not as violent......probably because the sprag helped hold it together, or the RPMs were not quite as high as other failures.
The reason the transmission fails has NOT ONE THING to do with the sprag. The reason for the failure comes from doing burnouts in first gear and having the tires hook up on the 1-2 shift. The resulting shock is what causes the transmission failure.
A manual valve body will totally eliminate the entire problem IF the operator will simply do the burnouts in 2nd gear. NOTHING else is required. No bolt in sprag, nothing. They are a nice addition, but the only one thing that stops the failure is the manual valve body that allows 2nd gear burnouts.
Make DAMN SURE you keep the tires spinning THROUGH the 1-2 shift. But that's still no guarantee.
I would think that line lock would help there because there will be less resistance.
Ted
EDIT:
My answers here are ASSUMING that you do not want to go to the expense of a billet front drum. They are about 600 by themselves. But if you do that, this will eliminate the problem providing you get the right drum that's rated for the correct RPM. But they are expensive. The cheaper way is simply use 2nd gear.
My answers here are ASSUMING that you do not want to go to the expense of a billet front drum. They are about 600 by themselves. But if you do that, this will eliminate the problem providing you get the right drum that's rated for the correct RPM. But they are expensive. The cheaper way is simply use 2nd gear.
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