Hi, Guys. I have an '07 F-150 4X4 with the 5.4 in it. It is rattling on acceleration and I cannot figre out where the noise is coming from. The guy that just put plugs in it says possibly a cat converter however it does not rattle under a power brake situation. Only driving down the road. The noise stops as soon as I let off the gas and does not happen at cruising speed. Only under acceleration. Checked all the heat shields-Nothing touching. Sounds like it is coming directly under the cab. Very hard to tell if it is the left or right side but sounds more like the drivers side. Any input would be appreciated. Thanks.

 

I would have to agree about the converter that is the same way my old Jeep acted up when the converter went out on it.

 

I had the same problem... after i put the rancho leveling kit and banks exhaust on my truck it was doing the same thing, i got my cats replaced under warranty and that wasnt it, in my case i had a broken vaccum line but it could just be a bad vaccum seal on the hub itself. put it in 4wd and see if the truck still makes the noise if it doesnt do it anymore that would be your problem, if thats the case all you have to do is figure out which side is trying to engage and check the vaccum lines and if they look good the new hub is fairly cheap and not a bad job. but being so new i would asume the truck is still under warranty so i would just take it to a garage...

For me when i was installing the leveling kit i moved the vaccum line on the passenger side to replace the nuts on top of the strut and never put it put it back in its holder away from the manifold. after jacking the truck up and finding out which side was trying to engage i found that it was the driver side hub, i took a vaccum tester and it held just fine, so i moved to the booster, and when putting vaccum on the lines coming out of the booster it didnt hold, so my dad blew about 10psi of compressed air thru the line and i traced the line and found the leak above the passenger strut fixed the line and no more rattle! Try the 4wd and see if it goes away. Good Luck!

 

Update on the "rattle". You were right about the vacuum leak. Found a broken fitting up by the firewall. Was trying to engage the passenger side hub. Thanks for your input-Would not have found that easy without it.