Went out this morning and the truck fired right up as usual. Listened for the knocking noise. Here's what I found out: It's come from the last cylinder at rear of engine. I only knocks when motor is reved-up but not at high RPM or at idle speed. Pulled the plug wire to that cylinder and it was more noticeable. I also got a slight shock when pulling that wire. The others didn't do this to me. Could be a bad wire or stray current as this wire is near the coil and starter wires. So is it a bad rod, bearing or what? P.S. Frank50 I bought this truck up by you at a lot in Staunton, Ill.