right rear metal to metal rattle sound

[a42l2011]

I have a rattle in the the right rear of my 2002 A8L everything passes visual inspection. I literally removed everything from trunk including spare tire, removed the rear bumper. I have changed out rear brakes and have eliminated loose brakes because I still have a metal to metal rattle sound with the parking brake dragging while I drive car over bumps. I removed the shock absorber and the noise was almost gone so I replaced with a known good one, same metal to metal rattle. Now the crazy thing is that I just bought a 2003 A8L with same noise! So I will tell you that I Have owned 2 97 A8s, a 98 A8, 2 2000 A8s, 2000 A8L, 2001 S8 and my current 2002 and 2003 A8Ls. Yes that is 8 D2s in the last 7 years. My best friend loves my A8L so much he bought a 2002 and his nephew bought a 2001 S8. So I have been wrenching on 10 D2s. I have never had this noise except these two cars. I need to solve this problem so I can sell my 2002 and put the smile back into driving my A8L. I don't have the special spring compressor or I would have removed the spring for a better inspection.
Any Ideas?