I just bought a 2005 Fx4 and I am hearing a faint very high pitched whistle when I accelerate. It is loudest when I am trying to maintain a speed. It doesn't seem to cjange with rpm. The tone of the whistle is pretty consistent. Anybody had this problem? Also the air conditioning unit groans a little when switching from Max AC to defros
t. It all works just makes noise. I am new to the Ford world.

 

my truck has a high pitch whistle to around 3-4000 rpm but its just air getting sucked in to the engine.

 

Any modifications...like CAI or aftermarket sound system?

 

I have the same thing going on. Mechanic friend said it could be many things. He said driveshaft/tranny possibly. I hear it the most while in cruise or holding speed manually via pedal.

 

These had a problem with the output shat bearing in the trans mostly with 4wd it's the very last bearing in the trans.

 

Also the blend door arm guide needs grease common on these

 

Mods: 3" space in front, K&N Intake. Has anybody had to replace the output shaft bearing? I am guessing it could be this because it only makes the whistle while in gear. The strange thing is that it sounds like it is coming from the dash area. I have had K&N intake systems on other trucks and this sound is not familiar to me.

 

So I think I narrowed it down to the intake. Has anybody had any luck getting rid of the whistle, with or without k&n CAI? This whistle is not normal in my opinion and is driving me crazy. I looked at a couple old threads about it but never found any remedies.

 

this may be a stupid question but seeing as your new to ford and you just bought the truck, is there a throttle body spacer on it by chance? if its not that then its just the intake. As far as the ac grunting i have a 2004 ive had for 3 years now and it does the same thing and its not an issue

 

could it be an aftermarket Throttle body spacer? Mine whistles when I go.