hoffmanfx4

I have a 2012 ecoboost SCREW, recently I noticed a rattling noise, almost like a can with some marbles in it. This noise starts at around 20 mph and contiunes as long as the engine is under load. If I let off the gas or shift in to neutral it goes away. And i can rev it up in neutral, and there is no noise either. I also have noticed that when I put the truck into 4wd that the sound goes away as well. Didnt know if anyone could send me in the direction of what may be going on with it.

Thanks

JCR 56

Sounds like an IWE.