It's a patrol thing mate, from what I've read there's bugger all that can be done.
People have said they can fix it with new "things" in the gearbox, but have then commented that the noise returns within about 10,000km. On the other forum there is talk about using different oils and/or additives in it which can help, search for "gearbox rollover". Lots of theories, not many consistent results unfortunately.
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