Vibration Under Passenger Floor

[tequilaman(Dave)]

Hello, I own a 2007 NBS Silverado Crew Cab, and was wondering if any one can explain or have the same problem. when i take off gradually i can hear like a metal shield vibrating under passenger floor, but then goes away. also everyone check the bottom door seal for trapped dirt or anything that gets caught up there. I had mud still there after car wash. very poor design of door seal. Just my 2 cents and my first post here. Very informational site here. Glad i found it..