I have this issue now. Its not due to the wheel slipping. Its a different noise. Im familiar with the wheel slipping and during searching for the rumble issue that alex has mentioned many people chime in to say its the wheel slipping issue.
Its slowing getting worse in my is300h. Rough ground, full lock, low speed seems to set this rattling going. Had a lexus technician verify its not the wheel lock slipping noise, its something else within the suspension or steering colum. Could even be drop links.
Im planning on putting it in for a check but at 190 an euro for diagnostics..... im holding off until i scour the interwebs for any else experiencing this or has solved this issue.