Grinding sounds can travel all over a truck from the source sometimes. We need to know a few things first. Is the noise consistent with road speed or engine speed? Is it tied to acceleration/load or coast, or "float" conditions? Straight ahead or turning? If you know the exact conditions when this happens,, that can help narrow it down! There's a lot of things that can grind on a 4x4. I had driveshaft splines make a grinding sound under Float conditions once (Not under load, not coasting, but in between).
