Recently, my 05 Lariat 5.4 4x4 has been making a whistling noise above 2000 rpm. It sounds like air leaking out very fast. It stops immediately after I take my foot off the gas, and it resumes the second the rev counter goes over 2000. The higher the rmp count, the louder the noise becomes. If anyone has any info that'd be helpful.

Thanks

 

Pull up your oil dipstick and see if the o-ring is intact on the yellow handle. The dipstick is sealed and without it, it can make a gawd awful whistle.

 

Alright, so I'm fairly certain that the noise is coming from my exhaust. Had friend sit in the back while I drove, and he said it sounded like it was coming from right underneath him. Anyone have any suggestions for figuring it if it is one and how to find it? I will go ahead and check the dipstick to be certain.

 

when you find it let us know. Mine does the same thing and I've looked at every vacuum line etc. and found nothing. I thought I found it once when I discovered a drain hole in the bottom of the air filter housing, but I plugged it and didn't make a difference. Mine isn't a specific frequency whistle, it changes with rpm and/or throttle position.

 

Went to the local muffler shop today.... Apparently my cats have gone bad and exhaust is flowing around bits of broken metal and creating that whistling or leaking noise.