Last night we were coming home and while the speedometer was at 45 it begin to climb up to 50 then to 55 when we had not gained speed. As we begin to slow down the speedometer didn't register the correct speed and when we came to a complete stop the speedometer still was showing around 20 mph. The truck is an 2004 4wd with a 5.4 automatic, anyone have an idea what this might be?

 

It could be your output shaft speed sensor, located on the tranny. I would think that if it was, you'd have some trouble codes popping up. They run for about $30-$40 and are easy to install. Might be a good place to start....

 

My speedo is stuck on max and clicking and I feel something rubbing under the truck.

could it be output shaft speed sensor?