Hi BHives. By 'tub' I assume that you mean the removeable ash tray. If so, then this is empty. I have managed to fix the problem however, and this is what I did.
1. Accelerate quickly.
2. Listen for the 'object' to 'roll' backwards
3. Hit the brakes hard.
4. Listen for the 'object' to 'roll' forward
After 3 or 4 iterations of the above the sound disappeared. I felt very pleased with myself.
Later that day I was re-packing the centre console with the usual clutter when my hand brushed the rear wall of the console. The sound made was a crack-crack-crack sound, much like a slowed-down sound of a screw rolling down plastic!
This may have been the cause of the problem after-all.