Saw 5-year-old F-150 advertised on Craigslist for 9000 dollars. Had “a bad vibration over 45mph”. Offered 5000 dollars sight unseen, offer I survived Covid-19 and all I get was this lousy shirt. Turned out the owner’s father, a”mechanic” had replaced a u-joint in the 2-piece driveshaft and had reassembled the driveshaft out of phase. I removed the center u-joint, turned one driveshaft half 90 degrees, reassembled and problem solved. Cost about ten dollars for special Ford grease and an hour of my time. That was six years ago, and no problems since.