cracked flexplate

[461cutty]

cracked two flexplates in two weeks. i think that it's vibration related, but can't figure out what could be causing the bad vibes. you can feel the car shaking through the steering wheel and floorboards. it only shakes when i'm picking up speed from a dead stop,or when i let off the gas and let the rpms come back down.anything over 2000rpm the car runs smooth. any ideas?

[LSx_88_Ciera]

On deceleration does it go away if you put it neutral? What about when you place it in neutral and kill the engine?
By the way I am thinking maybe torque converter.