Problem w/ Speedometer in 04 Chevy

[Primed67]

This past week my speedometer started messing up. I was on my way home on Interstate with the truck on cruise about 75 mph. I went to accelerate to pass a car faster w/out disengaging cruise. Once I passed the car my speedometer never came down. It was stuck and would go up but would not come back down below 45 at a complete stop. Over the weekend it dropped back down and was acting normal until my trip back to FW. Same thing happened but this time the spedometer continued to rise until it pegged out at 130 +. I come to a complete stop and it is at 75 mph. I don't have a clue what is going on but both times it has happened with cruise on while I was accelerating with the pedal to pass someone. I turned cruise off and still did not drop. Anyone got any ideas? I would like to maybe have something to tell the dealer to look at. Thanks in advance to any help!