I did a search and I am not seeing anything specific on this. I'm not even sure if I am on the right forum. But here goes....

I have a loud sound coming from somewhere on my truck. It is a loud hum. It starts at 43-45mph, and slowly fades out as I go faster. The sound is loud and just started about a week ago. If I coast there is no sound. If I hit the gas the sound starts. If I shift to neutral and hit the gas there is no sound.

I have a 2004 F150 Supercrew. It has 90,000 miles.

I've read that it could be the U-joints, drive shaft (that must or must not be replaced if you fix the U-joints, depends who you ask), wheel bearings, or a vaccuum leak.

I tried lifting the rear end of the truck and had my wife hit the gas - no sound.
I felt for play in the U-joints and there is none.

My dad thinks it could be the wheel bearings since the sound only happens when I hit the gas or a 'load' is put on the drivetrain.

I'm lost here. Any guesses as to what this could be?

Thanks.

 

Has no one had any experience with this? Any help would be much appreciated.

 

mine does the same but it has been doing this since i have had my truck.. 06 stx 4.6l with about 46,--- on it. nothin went wrong yet so it must be natural if we are speaking of the the same "hum"

 

i dont know if it helps, but based on your test, this "hum" only appears when the truck is moving. i doubt it's the U-Joints as they're stationary. have you tried checking your tires? they could be cupping. it could be the wheel bearings, but based on past experience the hum actually gets louder as you go faster.

 

Thanks for the replies Bewtew and Corycham. Yeah I just put new BFG T/A KO's on it. Had the dealer re-balance the tires. But now luck. Yeah I was leaning toward the wheel bearings too, but I figured the same thing as you with the sound getting louder... I may be stuck with going to the dealership and hope they don't screw me over............

 

mine gets louder with more gas and when i let off to coast it goes away.