I've done plenty of research. I am not a noob to the forum. I have a 2010 Ford F150 Platinum, 5.4 with 36,000miles on it. Not rebuilt. I get a rattling noise between 1,000 and 2,000 rpms. It does not rattle when giving it gas, let off the gas, or braking. It just randomly starts and stops while driving. I have searched the whole underside for loose pieces or heat shields...none. The noise doesn't go away if I press the Tow/Haul button, the noise is still there, but if I put it on 4x4 High it goes away. The noise appears to be centered around the front of the truck. I used a stethoscope and don't hear anything out of the ordinary, although I can only use it at idle, in park with the hood up. The IWEs don't have any water in them. The IWE vacuum lines are not brittle or cracked. My complete exhaust system is tight- no loose bolts. The link takes you to a video that is very similar to mine, but the video doesn't actually say what the problem was... a lot of guesses. Any help would be greatly appreciated. If I can fix it, I'd rather do it myself than pay someone else to do it. https://www.youtube.com/watch?v=g_QoOZbm46w

 

One of my old guidelines is that if I can't diagnose a noise, I let it go and if it's serious, it will get worse and will be more obvious to troubleshoot. Sorry I can't help.

 

Too add... I am not getting any codes on a reader. The noise is not a little noise. It literally sounds like I am dragging a chainlink fence. Also, I have noticed that at low speed in 4x4 High the rear tires seem to bind, almost drag.

 

You know that you are not supposed to use 4WD while on pavement, right? It binds the front when the truck turns.

 

Yes. Only trying to paint the picture on what is happening with my truck. It was on a dirt/gravel road.

 

Problem solved and spent way more money than I wanted to. Replaced d/s IWE. Noise still there. Replaced vacuum actuator. Noise still there. Replacing p/s IWE, the vent and vacuum tubes fall out of the cable sleeve. Both were completely pinched off with no damage to the outer sleeve. Bought some new hard vacuum tubing. Took it for a ride and noise is gone. BTW... not sure if it is by design, but the OEM hard plastic vacuum tubing is very brittle.

 

Thanks for letting us know what solved the problem

 

I was going to say, the vacuum lines. I have a 2010 with about the same mileage and I'm loosing vacuum when pulling steep hills. I bought a vacuum tester just to double check but haven't gotten to it yet. Any tips?