Is the truck auto or stick? My Manche had a squealing belt, or so I thought. I replaced the belt and all was quiet for a day and then came back. I then replaced the idler pulley. Then the PS pump, and then another belt, but it just seemed to get worse. Sometimes it would be quiet until I pressed the clutch, which made no sense. I had a hunch one day and had someone else press the clutch and I witnessed the crank pulley move ahead 1/4"-3/8". I next replaced the engine and the noise was gone. I hope you don't have the same issue as it was more work than I needed.