What is this: odd solid steel block mounted to frame?

Found this random solid steel block mounted on top of the frame under the driver side of the bed behind the rear wheel. What is this for? Corrosion inhibitor of some kind? There are no wires or anything going to it. Just dead weight. It's mounted with rubber bushings but they are very loose and this thing flops around bad. Could this be something causing a clunking noise ? Anyone know what it is of if it is on all trucks. You can see it best if you have the spare tire removed

Has been asked here in several threads and for years.

http://www.fordraptorforum.com/f5/identify-part-underside-bed-box-vibration-damper-18972/

http://www.fordraptorforum.com/f9/wtf-10727/

RDFTS said:

Has been asked here in several threads and for years.

http://www.fordraptorforum.com/f5/identify-part-underside-bed-box-vibration-damper-18972/

http://www.fordraptorforum.com/f9/wtf-10727/

Click to expand...

Thanks