The Rotating MASS of the 727 Drum is why it explodes when the Sprag rolls over. The transmission will rev 2.2 X Faster than the engine RPM so around 14K RPM the 727 Drum will usually come apart. The 904 does not have the same problem because the Drum is not as big or heavy and can take right around 20K+ RPM before it fails. I have yet to see a 904 come apart from a front drum explosion. If anyone can prove different please have at it I would really like to see one.
