Explain 'forever'. Are you being sarcastic? or does it just not shift as hard?
For what its worth, my 3500rpm footbrake/3900rpm flash dynamic converter seems to 'stall' when i shift hard, vs my cheap 2500 that was in there. Doesn't effect the speed of the shift it seems, its just for a split second. Does it seem like it may just be stalling/flashing the harshness of the shift, dampening almost. I've talked to a few other guys about that and they both had similar results..
Also do you have a factory cooling system? Is it a off the shelf or tweaked to spec converter?