if this is an automatic. i have seen this exact same problem and it is caused by the driveline failure or shock load from the diff breaking. the pump output that holds the direct drum sometimes will get a crack in it right behind the selectable thrust washer. it works when the fluid is cold but not when it heats up. pull the pump and check the area right behind the pump. also check the hardend race and the roller clutch on the direct drum. hope you find it. theres nothing worse than racecar gremlins.