It’s an M6 nut that holds those brackets in place

 

There are trailing arm bushings.

 

Thanks, Ill check it all when it stops raining soon

 

I’m gonna say most likely the pieced together exhaust pipe, a heat shield might have broken loose.

 

I didn't hear anything while shaking the hell out of it te other day so not sure... Now today I went to the store and back in the rain, didn't hear that rattle??? maybe it was that plastic thing on the battery cable next to the body, or some reason it just didn't rattle today? hmmm

 

Might be it took the weekend off! Keep us posted!

 

When mine was new I had all kinds of annoying small rattles, thumps and bumps from the rear of the car. I found that the rear bumper cover and it's attachment points of those plastic pins was a poor design.
I wound up replacing many of those pins with small screws and nuts. And even wedged some foam strips between the inner metal bumper and the outer plastic fascia. Quieted up most of the noises I was hearing.

 

well, so far that rattle is gone, It was that ring thing on the neg cable off the battery that was rattling on the body ( I assume since it stopped after I flexed it over a bit ) so 2 days no rattles, Im happy !
Going to the DMV in the morning to get the HHR legal since they are finally opening ( unless they change the date again, but was told last week that Monday will be open !