Need advice with tranny replacement
 

My fiance's 2000 Taurus SE (3.0 V6 with 24,000 miles) is fixing to have a new transmission installed. After three visits (1-PCM replaced, 2-valve body replaced, 3-torque converter and fluid flushed), it is still shuddering when shifting from 3rd to 4th.

What I am wanting to do is to try and get the dealer to fork over an extended warranty to go along with it. Does anyone have any ideas, tips or ammunition to use for this. I am afraid that a new problem might not show up until after the 36,000 miles is gone.

Thanks