Humming noise -- help!!!

[cdelap]

As I got about 15 miles from home after a 600 mile pull with my 8k fifth wheel I started to notice a bit of a hum coming from the rear end of the truck I am not sure where to start looking, could be heated brakes, a rear diff or even transfer case. I have let the truck cool and unloaded it. before taking it for another quick spin. the noise increases from ~10mph till 50 or so before I don't notice it over any of the other truck noise (wheels and motor). IS there a place to look first with the truck, I don't feel that it is trans related because shift points do not affect the noise whatsoever. at first recognition it sounded like possibly a wheel bearing on the trailer or brakes not releaseing on the trailer unfortunatly the trailer is fine and the noise in in the back of the more expensive vehical

Any help will be greatly appreciated.

[jesilvas]

Check the ujoints.

[cdelap]

Wouldn't u-joints make more of a rattle or vibration? Not that I wont check them, just curious, I am kinda thinking it could be a carrier bearing which could have failed due to u joints

[dee004]

Is it still there if you let of the fuel pedal and drop the transmission into neutral while still coasting along?

[cdelap]

yes it is, it doesn't really change pitch when I do it

[dee004]

Originally Posted by cdelap

yes it is, it doesn't really change pitch when I do it

Not my truck but I had the weirdest hum coming from the passenger side rear of my Jetta a month back. Same symptoms as your experiencing. Started at about 15MPH and got louder and the frequency picked up with speed. Stayed the same if I hard turned left or right and coasting engine off in neutral. I checked everything and it ended up being a wheel bearing. I've changed out many a worn bearing in my time but never one that sounded like this one and when spun by hand wasn't dry or any gritty feeling and no play in it like they normally have. Three tiny little imperfections in the race.

[cdelap]

After putting a sonic ear on the truck, I am leaning towards wheel bearings, i may have a pinion bearing going as well but can necessarily tell until I get these wheel bearings going I tow with a 80 HP custom tune on my edge ... could this add wear to the pinion bearings?