Somewhere between 400 rpm less than stall speed to just pull the chip out and go against the converter for your best leave on a .400 Pro Tree. My 400 is chipped to 6200, shift at 8200, I can red a .400 Tree if I really want to.

1994 Undercover Chassis 125" altered stack injected big block, soon blown and injected Member of The Torque and Recoil Club