JohnM....I fixed the rattle in the back of my car today. It ended up being the driver side "anti-rattle" spring on the caliper assembly. It had lost the tension so I removed it, rebent it, replaced it...rattle gone!!! I also adjusted my parking brake on both sides as well. That is when I realized the rattle did not go away and used a rubber mallet to figure it out.

Part I rebent:

http://www.*********.com/catalog/199...le_spring.html