Yesterday I had another 904 tail housing crack. It did it on Memorial day and I simply swapped the housing hoping it was a fluke. Guess it wasn't.

I plan to have the alum shaft checked for balance but I also want to check slip yoke engagement. What is the ideal distance from the end of the tail to shoulder of the slip yoke?? Could the slip yoke not be inserted enough cause my problem??

Anything else I should be looking into. The engine is on stock rubber biscuit mounts that aren't torn and has a stock rubber tranny mount.