Maybe its something with the hydraulic clutch? I'm using the mechanical clutch linkage with my Keisler/tremec setup in my 340 challenger and have had no issues while shifting at 6500. I'm also making quite a bit more power thanks to 15psi of boost and its holding up quite well. I do have a custom hydraulic setup on my scamp that I converted from a A904 to a A833OD and it doesn't like to shift nearly as fast as the mechanical linkage does.

-Jon