Reference this thread:
https://www.ford-trucks.com/forums/3...-up-noise.html

I was helping the OP diagnose this noise because I was trying to figure out what would cause it. Turned out the roar in my engine came back last weekend after I got stuck pretty bad and had to rev it up to get out.
The intake tube vibrates during the roar - almost like the sound and vibration of a loose bearing at high RPMs - and when the engine begins to idle back down, it quits.

This same "roar" occurs in gear on the road at lower RPMs. I'm stumped.

 

Have you checked the center drive-shaft barring? I had to put the truck on a lift and then put the truck in drive to identify the problem. It can roar and make different noises at different speeds. It's easy to check, hope that helps.

 

my power steering whines really loud when cold, dosent shake tho

 

It can't be the carrier bearing and this roar happens during cold weather or hot, or if it has just been fired up or has ran all day.

I can lay my hand on the air box and feel the vibration.

Thanks for the replies!

 

Check the Harmonic Balancer and the Clutch Fan.
Some times viberation in the very front of an engine will send weird sounds all over the place.

 

Harmonic and Fan in good shape.

I am begining to think that it's air passing by the throttle plate. Could be a sign that the TB needs a good cleaning.

 

I have another thought, sometimes a broken exhaust stud/studs can cause this. Excapeing air can as we all know make weird nosies and of course air will creat viberation which translates into noise.
I don't think it would be a waste of time to check the exhaust manafold studs.

 

No, not the studs, but I appreciate the feedback.

If I get off work this weekend, I may tear into the air box, clean the MAF sensor, check the throttle plate and look for any build-up. Will let you know.

Thanks for the replies!

 

Bump

FYI - the "roar" develops between 900 and 1400 RPM's, but not constant. The most frequent is between 1150 and 1250 RPM's. This is load or no load.

Still waiting for time off to check it out.

 

It would be nice to know where the problem is, and the cause of this roar.

 

Check the black cone on the air filter, to see if it is still attached. Or has it been sucked down the air intake to the throttle body?

 

My bad! The black cone on the air filter element would not make its way to the throttle body but be stopped by the MAF. Still causing a turbulence in the air flow and a possible noise in the air intake.

 

Sorry guys - just got one day off this weekend and my wife made me take her fishing...

But I am not driving it until I can find the problem.

 

Its your Belt Tensioner Pulley thats doing it. Mine did the exact same thing. Changed the tensioner and it fixed it. Nice and quiet again. Its pretty cheap and easy to change.

 

Your fan kicking in? If your're really hitting it, it would explain the roar in the low rpm's while the fan is engaged.