The stock TC has a cheap stamped cover. With stock HP, it will usually hold up fine for the life of the transmission. When you raise the HP & torque, the extra twisting effect will distort the cover. When that happens, your lock up clutch dimples & only makes contact on the high spots. Then, it starts to slip, turning the contact areas blue, and flying the fluid, raising overall transmission temps. This can only go on so long, and you've destroyed the TC. Then the powdered lockup clutch debris circulates through the system reaking havoc. My particular TC has a solid steel, non-flexing, machined out billet cover, a stator milled for a stall speed of about 1800 RPM instead of 2400, and the triple disc clutch pack, that is supposed to hold about 500 HP with stock line pressure, without slipping. I can't make it slip with 300 at the rear wheels, & Lord knows I've tried.