I have this rattle that only happens when I go over slight bumps, and it'* driving me crazy, it started about 3 weeks ago.

I took the rear tire off and check out all the under carriage and found nothing that would cause the rattle, mainly focusing on the Strut, but found nothing.

I also took the door panel off and check to see if the window was loose, but it wasn't. I also checked the Door Latch and Anchor, all were tight.

Took the rear seat out and check the battery, and seat belts, nope....

Looked in the trunk and check the Top Strut mount and speakers, nothing.

I just can't seem to find it, and I'm hoping that someone here may know what I'm dealing with and can help, because this is driving me nuts..

Moved to 2000-2005 Bonneville thread where it will get more views and responses for the rattle issue.

Check the B and C pillars and any other trim to make sure they are tight.

The Plastic panels above the rear deck and between the fron and rear doors seem to be tight, I even checked the drain tube for the sun roof (short from taking the head liner down), and cable tied it to the wiring harness in the trunk. My father has a 2001 Buick Park Avenue, and he is getting the same rattle, I'm thinking this is common on the GM H Bodies.

You check your exhaust?

Exhaust is fine, tight like the day it came off the floor.

I took the rear Pillar cover off and found that the drain tube for the sun roof was loose, so I cable tied it to some electrical wires and it seemed to quite it down, but wasn't the issue.

I found that the rear Stabilizer links needed tightening, which eliminated some more rattle, but I think the Stabalizer Bar bushings need to be replaced, which I think are Polyurethane, or Silicone, not sure if they're rubber. I think a 2005 should need these replaced so soon, the car only has 65K miles on it..

Hey SLE2005,

I had this same issue when after I purchased my car. My parents live on a gravel road and I would hear a slight rattle coming from the right rear of my car as well.

I took it to the dealer to have it looked at since it was covered under warranty, and they replaced both (left and right) shocks and mounts in the rear and this took car of the problem. I would suspect this is the same issue. I did the same easy checks as you, and everything seemed solid to me. I'm not sure how to determine if there bad as I looked past them but the dealer identified it and solved the issue!

Found out that the Sub-Frame mount just in front of the rear wheel was loose due to Salt corrosion, I torqued it down and all is well..