my trucks an 05 f150 lariat. going down the road i have a real loud high pitch wine coming from the rear. its not always loud either which is why i think its the fuel pump. i can be going down the road 55+ and left off the gas and the loud humm fades out quick as i can feel the truck let off on power. i push the gas again and the sound comes right back. i already changed out the fuel filter as i had hoped maybe it was plugged up but the filter was fine. it seems that today the noise was progressively louder than yesterday. i searched thru alot of posts on here and alot of it is loss of power or cutting out. im not experiencing that. just a really loud humm also like a wear(ing) noise. like taking a wheel bearing with no grease and putting an air nozzle to it. just in a deeper octive. only when i push on the gas. when i let off and there is no demand for alot of fuel the sound diminishes. i dont know if it completely goes away just low enough i cant hear it. any help with this is greatly appreciated.

 

rear end or pinion...

 

wow...thank you. i didnt even think about the pinion gear. head in palm.

 

makes more sense to me than a fuel pump...

 

after reading your previous i went out and started it up and there is no whine noise coming from around the tank so i pulled out and boom there it was as i was going down the driveway. makes sense now. thanks a ton. now i just have to figure out how im going to press some things out and on. im just gonna rebuild the rear end. it has 170k on it so...wth

 

i put up a video. its kinda blurry when i show the front of the casing but you can see the front of the pinion by the bearing moving in and out in a wobble fashion. alot of oil around the front to.

 

nice.. now lets get her fixed...