Could be that someone put a 6 volt car starter on a 12 volt truck.The flywheels have different number of teeth.That would cause grinding when engaged.
_____________ Floyd If we choose being kind over being right,we will be right every time. Knowledge is a poor substitute for experience. Remember what is precious to another, may not be to you, but it is precious nonetheless. 1948 Chevy 2-Ton | 
