Drivetrain Damper
WARNING: This page is about a different car, the 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, 2004 Ford Excursion, and 2004 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
A weight attached to the engine, the transmission, the transfer case or the axle. It is tuned by weight and placement to absorb vibration.