Mitsubishi Triton whirring noise when deaccelarate

Whirring noise that is intermittent, starts when I shift from 3rd gear to 4th but it's very feint until I downshift into 3rd. This is when it gets louder and changes pitch/speed depending on what hear I use. it only stops when vehicle slows to a crawl but doesn't need to completely stop. With the clutch in or in neutral it goes away when doing estimate under 5km/h. When it does go away there is a little bit of a clunk. ODO only just ticked over 80,000,i dont do. any off road driving it just seemed to start randomly.