Rattley auto box. 2002 v6

[skater]

When first driving away I hear a rattley noise in 1st and as it changes to 2nd.
Have checked the level when warm, in P, engine running. Topped it up a bit with D lll. Colour is pinky.
Once warm the box is quiet.
Always changes smoothly, possibly even better after the top up.

No doubt a drain and re-fill wouldn't hurt but could something be loose inside, relating to 1st/2nd?

Thanks for any help,
James.