For awhile I have noticed that my speedo stops working. Its usually when I get into the the gas pedal hard. Any ideas as to what could be causing this.

 

03 and up are known for cluster problems...

If that's not the case, it could be a bad wire or speed sensor in the trans. You may have a loose connection that loses contact when the engine torques when you punch it. You would think that would throw a code hopefully though.