2002 renault scenic 1.6 auto noise

hi



great forum so helpfully and really appreciated!



we own a 2002 Renault scenic 1.6 auto with the DPO gearbox and it has recently developed a rattle when D is selected. If I put the car into N then noise goes, comes back when switching back to D



The noise is a tinny rattle but only happens when a gear is selected as mentioned above.



There are no warning lights light on the dash and the gearbox behaves normally.



I've had a look to see if anything is touching/out of place etc but cant see anything.



the gearbox fluid has never been changed, would this be the best place to start?



I don't want to ignore the noise in case it gets worse.



any idea's guys & girls?



thanks