Im going to start this off by saying I know very little about trucks. I have an 04 f150 FX4 screw and today I noticed a horrible screeching coming from my driver side. So my mind went instantly to breaks. But they don't screech while braking, just driving. And what puts me in a bind is I have to leave out of the state for work in the next couple days. Any help would be greatly appreciated.
And Idk if it matters but engine is 5.4 3v

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does it only screech when ur on the gas at certain times???

 

belt...

 

It screeches like a banshee while on the gas. Not nearly as much on the breaks. It's loud enough I can hear it over the engine while drivin

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But it don't screech while idling or in park

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if it only makes noise when ur on the gas at certain times its ur 4wd vacume solinoid. its a $16 part. its located on your fire wall behind your battery. its a black plastic circular canister only an inch in diamiter and maybe 2 inches tall with a electrical plug and 2 tiny rubber hoses connected to it. if u cant fix it right away, then follow the one tiny vacume line going from the solinoid to your intake manifold(the line going toward your engine), there is a check valve(its black on one side and white or red on the other and its circular). this will be located about half way on this vacume line. if u pull the hose off of both sides of the check valve and plug or tape both open ends of the hoses the noise will go away. all this does is cuts off the vacume to your 4wd hubs which will now b locked in at all times until u fix the solinoid. its safe to drive like this all your doing is pushing your front axle without engauging the 4wd you might lose a little mpg but you wont notice it. when you do fix the solinoid make sure you install the check valve the same way it was on the vac line before.!!

 

i forgot to tell you an easy way to find out if its the 4wd vac solinoid. if the noise goes away while your driving in 4wd then its def the 4wd vac solinoid. just a reminder dont drive in 4wd on pavement if your gunna be doing alot of turning make sure you only test this theroy on a straight away for a very short amount of time.

 

Thank you for yalls insight. Its too late right now but ill try it first thing in the morning when I wake up

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so did u figure it out? did the noise go away when you had it in 4wd???

 

No it didn't go away. Also changed brake pads again and looked at rotors but im out of tha state for a couple months so ill have to have it looked at :-(