It is not unusual for a Torqueflite 904 converter to crack the pump drive neck as shown above.  Turbo Action to help stop this problem, was the first company to use chrome moly pump necks.  This helped, but you can help this problem even more with our help.  Machine the ring on your reaction shaft off and then request to make your converter pump neck solid on the inside (N0 Step).  If you machine this ring off and you do not make pump neck thicker, you will not hurt your transmission or converter.  If you install a solid neck converter on a stock transmission, you will have problems.