This started a couple of weeks ago and was only happening on acceleration when lugging a bit in high gear like on a long hill, I would hit the O/D button to drop a gear and sound disappeared. now it has gradually gotten worse. It is there almost all the time when cruising.
I crawled underneath and found that I do have a leaky right rear outside axle seal, but I do not believe this is where the sound is coming from.
If you have ever heard a bad d/shaft hanger bearing this is a very similar sound, any help appreciated, thanks all
OOPs sorry 04 screw 4x4 5.4 auto

 

Sounds like preignition to me try running a higher octane fuel. What mods do you have

 

no engine mods, i don't think its pre ignition as this 04 has 280,000 kms and have never had this issue before. just sounds more.....mechanical than that if that makes sense

 

going to put it up in the air now and have a real close look, but dang jack just broke going to run out and buy one quick

 

Let me know what you find Tapdog. I have a similiar noise but mine is only when I haul my trailer and only going uphill, as soon as the tranny kicks down it goes away (Overdrive off). Got under mine and looked around but couldn't find anything that looked out of the ordinary.

 

I would still try running a tank of premium in it and see if that fixes is, I haveheard a 5.4 preignite before and I thought the wheels were. Falling off

 

I am hearing a similar noise coming from the front left. Haven't had a chance to look into it. Let us know what you find.

 

Try putting it into 4 wheel drive when it makes the noise and see if the noise dissapears.