Rebuild 904 or swap for 727?
It's not my job to care about my customers' well-being. IF they want to play it safe, then buy a volvo with the extra side air bags. I'm here to help make their car a very dangerous piece of transportation from one stop light to the next. If they die, they die; as long as their transmission doesn't die. You're showing pics of 727s that were destroyed by god knows what; but pretty sure it was a lot more power than what 99% of small blocks put out. Too bad chrysler never put the 904 behind bbs so we could have a realistic historical comparison. Why spend money on a hardened 904 input shaft? and don't forget that when you want the right return springs on your 904 direct drum; that you can find somebody who knows wth you are even talking about. Most guys that come to me are just glad they found somebody who knows ANYTHING about performance TFs, and isn't trying to "upgrade" their own wallet. You know tons about these trannys, but most of it doesn't apply to 95% of the dudes on here who just want a weekend warrior.
Ok finally you have made a realistic post. Yes a guy that is just looking for a reliable economical build would be looking for a guy like you that just charges a fair price. I get that. Kudos to you.
I spent the money on a hardened input shaft because of my anticipated performance level.
That may be the first area of weakness. Ati transmission built the 904 for the first Chrysler drag pak. At that cars performance level the input shafts were failing.
I cannot confirm this story, but rumour is that when Chrysler was building the hemi super stockers back in the 60,s, they built a small number of them in Canada with the 904. NHRA would not recognize those cars.
Hence the birth of Protrans who began putting the 904 guts in a 727
To get around the rules.
The pic in my last post( not the Chev) are what happens to the stock drum at high rpm in first gear if the sprag is unknowingly failed.
The planetary gearset is designed to spin the front drum at an rpm
That is within its safe operating rpm. But this safe rpm relys on the sprag to hold. If the sprag does not hold, a new ratio is created
That spins the drum way past its intended safe rpm and centrifugal force
Combined with the material of the stock drum, becomes a grenade as the drum flys apart. That is why I said that it's not a horsepower issue. There is a member on here cracked back I believe that said that he had a station wagon towing a trailer and the drum exploded.
It would be very very rare for it to happen in just a daily driver.
But in a performance car, where you know the guy is gonna do bunny hops on the street and the like at any significant rpm,
The stock drum can be very dangerous. That's why locomotion recommended that a performance street car should use a valve body with low band apply. This problem with the 727 is so prevalent that John Cope racing will not make any of his performance valve bodies without low band apply. Low band apply uses the rear band to assist the sprag in holding under high torque so the sprag cannot fail. But there were many performance valve bodies made without low band apply. On the street if the guy is gonna goof off, he should have low band apply.
I have seen 14 seconds cars go up in flames when all the trans fluid got on the headers. Guys have lost feet, cars ruined, windshields
Broken. You have to have seen one let go to believe it.
They look jus like in that picture.
