well, a followup -it's now been 3 days since the fix was done on my tc (for the hatch rattle). To recap, the fix my dealed did involved the following: removed black trim piece from inside of hatch, padded with felt insulation and replaced, tightened trunk latch. So far so good - although on a side note, I noticed this morning that I was hearing a lot more road noise then usual out of my drivers side window. When I got out of the car I noticed that the black rubber "weather stripping" above the window had fallen out in one area. I tucked it back in and all is well but I'm just wondering when that might happen again...

 

Hi, I wondered did you figure out how to fix the noise?
I found my rattle was actually inside and part of the plastic that is the attached to the hatch around the window, It is a poor design . I had a 2005 prior to my 2015, both have the same plastic that wants to fall off and squeaks and rattles if it does remain in place.
i applied gorilla tape and it held somewhat deadens the sound.
Now the latest bummer is the front door speaker rattles like it’s blown. The whole car is a piece of plastic and it’s cheesy but looks nice. The 2005 was actually easier to see out of and the ground effects on the newer one seem to slow it down and they hit in areas if you aren’t careful.
Overall the Scion TC if you get a runner - will run upwards of 400k miles. Not bad on gas and a pretty decent price.

 

There are two rubber bumpers at the bottom corners of your hatch door. These bumpers are undersized and too soft to support the heavy door. Simple furniture pads will fill the gap that allows the hatch to clunk. You only need two. Stick one pad on each divot in the bumper cover. This should help. I did it about ten years ago and it's still working.