My 94 diesel 4 track makes a 'ting' noise coming from the font of the prop, when I change gear .I have had a mechanic look at it,who says the noise is 'cos there is a bit of 'whip' in the box, and that is making the prop go 'ting'.I am not mechanically minded, and he said something about the cogs being worn and not meshing properly in the box. I asked him how long this could go for before something serious happens, and he said 'how long is a piece of string'. He was also vague about what the serious event could be.He said some of his customers have 4x4 vehicles who drive them for years with various clunks and noises coming from them. Anyone have any helpful comments? Steve