There is quite a bit of voltage generated when moving the steppers by hand. did you follow the instructions? did you remember that one coil on an adjacent stepper must be reversed since the motors move in opposite directions for each side of an axis. NOTE: do not move the steppers manually once hooked into the arduino/ramps or you could fry your electronics. the grinding you hear is most likely because you’re steppers are trying to spin against one another instead of with one another. and if you just have wires handing loose, and any of the coil wires touch it will cause your stepper to halt when you try to move it.