I have been trolling this site for awhile and yesterday I finally got an F-150. It is a 2004 SuperCab 4X4 with the 5.4. It was a one owner with only 65,000 miles on it. The only problem with the truck is that there is a slight humming coming from the rear end, it only does it when going at a constant speed. As soon as I get off the gas it stops and as soon as I accelerate it stops therefore it is not the tires. It has a 3.55 open diff if that can help. Does anyone have any advice to stop it, the noise doesn't bother me I'm just afraid it may be causing damage. Thanks.

 

Mine did the same. It was the pinion bearing had gone bad. 04 FX4

 

I recently replaced a bad pinion bearing. I had a constant noise in the rear end whether the truck was under power or coasting in neutral. Obviously, it was more distinct in neutral.

Sounds like it only occurs under power from your post. Maybe a u-joint? Just a thought.

 

Subscribed. Mine is a sort of a high pitched whurring sound. I gotta look at my stuff when i get back but ive been driving smokey mtn roads for 2 days now.

 

x2 for the pinion bearing

 

If you dont mind me asking how much did it cost? Also did you do it yourself or take it to a shop.

 

Mine does the same thing. I think its just how these trucks sound. But i also do have a constant humming that i know is the bearing. Similar sounds but yes one is only when driving at constant speeds and goes away when i either let off the throttle or accelerate while the other occurs all the time. I can feel vibration in the pedals which i believe is from the bad bearing.

 

Interesting. I have no vibration in the pedals at all. Other than the slight hum the truck rides perfect.

 

Than I don't think your bearings are the issue. But who knows. Lol

 

Just realized that someone mentioned it being the pinion bearing, I thought it read wheel bearing. Lol that could certainly be the cause. Man and I thought it was normal the whole time!