Let my try to explain what has happened. Up to this point, I have had no trouble with this vehicle. Last week my son took the boat to the lake and called and said the truck wasnt running very well and would not gear down when the pedal was pressed. He said he could only go 40 mph. When he got home, I could hear the fuel pump on the frame and to me sounded liked that was my problem. I drained the fuel bowl to relieve pressure, however, when the valve was opened, it didnt drain until I took the top of the housing and pulled up on the filter. I change the pump and thought all was good. Drove it up the mountain pulling a small flat bed trailer with portapotties on it and it seemed to be fine. Coming home after four days and 160 miles, all of a sudden it started to act like that again. I pulled off the freeway and checked my new fuel pump, all was good. It would idle and clank just like it does when it has run out of fuel until all the air is gone. So I turned it off, drained the fuel bowl and started it. It was only about 30 seconds when it smoothed out and sounded good and it got me home the next 20 miles. It has been a few years since I dropped the tank and cleaned the screens in the sending unit. I put in a new fuel filter a few months ago. I am going to pull the filter out and see if anything is visibly wrong. I wonder if its time to dropped the tank and clean things and also do the mod. Any thoughts?