2011 F150 5.0 4x4 leveled on 35x12.50s.
I was filling up at a gas station today and as soon as I pulled out my truck starts making this nasty rattle when accelerating but stops as soon as I let off the pedal and sounds perfectly fine at idle/in park. It seems to be worse in the low rpm range and usually stops when the rpm’s reach 2k while at cruising speed. Any accelerating from there though will cause it to rattle again. I’ve researched into the IWE issues but I locked it in 4 high and the noise continued and to me it doesn’t seem like the same noise from what I’ve heard in videos from folks who have the IWE grind. If anyone can point me in the right direction I’d appreciate it.

 

Check your heat shields out. They tend to make rattling noises in the lower RPM range. I have one on my 13 5.0 starting to rattle that I can see from the passenger wheel well.

 

I don’t believe it’s heat shield. I had a heat shield rattle and welded it up already and this is much more intense and heavy than a heat shield rattle. trying to figure out how to upload a video on here.

 

I was just about to edit my post and see if you could provide a video. You need to upload it to YouTube and then share the link here.

 

 

Meh, crappy gas, used that station before? are you using 87? was the tank almost empty when you filled up?

Everything you're doing seems to confirm it's pinging (knock)

 

I agree with MaDMaXX.
sounds like a bad case of pinging/knock.
I have had that issue even running 93 sometimes though not as bad. Change gas stations and avoid the low rpm high load situations that are causing it for now. Top if off with some premium.
You may have a bad spark plug or carbon buildup that is making the engine more susceptible to pinging by creating a hot spot.

I'm not sure why the knock sensors can't seem to do their thing.

 

No I never used that station before and yes it was almost empty. It took 34 gallons. Did not appear to be a high volume station. Should’ve known better but was the only station for quite a while.

 

Double check for any pending codes that haven't caused a CEL yet.

Could also be an exhaust leak - those can show as a tap-tap-tap or a chuffing sound.

 

Update: checked for any kind of codes and came up empty. Now on start up it idles very rough like it wants to die for the first 3-4 seconds then idles normal. The noise remains the same.