2011 S40 T5
I had a rear end rattle that I could not find the cause. Removed all the items from my trunk....checked suspension parts.....shocks etc....
I found a similar post for a different car that referenced loose brake pads could be the culprit.....discovered after some other research that the Volvo S40 should have a spring on the interior brake pad to keep it in place. I discovered that my car had the brake pads reversed.....the spring was on the outside brake pad. I reversed the pads on both rear brake assemblies............no more rattles!