Bowling Ball in my trunk?

[old frank]

Hi, First Post here and naturally I have a problem.

2007 Grand Marquis 35000 miles.

Several times on the first start of the day and backing down my driveway, it sounds exactly like something heavy is rolling around in the trunk.
We searched the trunk, definitely not anything there.
I recently had the wheels balanced and looked at the front and rear brake pads and they looked good.
I don't think it does it any other time but the noise has only happened twice that I noticed. I rarely drive the car and don't think my wife heard it before either but....you never know.

Any help on this one? Thanks!

[Hollowcreek]

Two things that I would check, but if its only got 35K on it neither should be the cause.

1. Make sure that there are no exhaust hangers broken or missing that are allowing the tailpipe to come into contact with the undercarriage. This did happen on my 2000 MGM and it did sound like something was rolling around in the trunk.

2. Check the rear brakes. Maybe something is loose?