Don't laugh at my description, but that's the only way I can think of to describe it. It's not very loud, and I can only hear it at highway speeds (60+) and it seems to quit when I let off the pedal. It seems to be coming from the engine somewhere.

It oscillates high to low, kinda like "waaaooo,waaaooo,waaaooo".

I SAID DON'T LAUGH!

 

I think Pachino said that, "Scent of a Woman" Anyway, is it from the engine or is it an exhaust drone?

 

Tires dude.

Been there, done that.

Put new skins on, smooth as silk. No more "Al Pichino"

Might be other causes, that was mine. JM2CW

 

On the 99's there is a TSB about this problem, it is related to the water circulation for the heater. It involves swapping out a T in the line or housing or something like that, can not remember the exact part swap. I suppose if I go look it would come back to me.

 

BDR2500...It's coming from the front and doesn't really sound like exhaust.

Tazman...My tires only have about 10K on them. I though tires too, but the noise stops when you let off the pedal.

Thaks of the responses,

 

bluebull...I had that replace way back at about 20K miles. I'm at 147+ now. It's been five years, but I seem to remember it being more constant and a higher pitch. Thanks for reminding me, it's worth checking again.

CR

 

Hmmmmmmmmmmm, musta hit the wrong button....again.

 

"oscillates high to low, kinda like "waaaooo,waaaooo,waaaooo".

Sounds alot like my wife complaining!

 

I thought about that too, but she hasn't been in the truck.

 

May be a bearing in the tranny???

Any noise from other gears???

 

Only at 60+ in #5.

 

crobtex,

This may sound silly but it also contributed to the exact sound I had.

Believe it or not, my transfer case shift **** became loose. Not fall off onto the floor loose but loose enough to turn by hand.

Even if I re-tightened by hand it would vibrate the way you describe. It wasn't until I took a wrench to it and snugged up the jam nut did it stop.

Silly but worth a try (and free).

Good luck

 

You check the oil levels in rear end/ft. end and trans, any leakage? I'd still bet on a mainshaft bearing in trans, could be a bad U joint somewhere too from description of the noise. Any vibration?

Brainstormin things you already thought of I bet huh...

 

Thanks guys,

I'll check the **** today.

It's been too cold and WET to crawl under the truck and do a really good inspection. Initially, I don't find anything loose, but I'll check closer when it drys up a little tomorrow. The diffs were changed this past summer, and I don't see any leaks anywhere.

 

Well, I'll add my .02.......you may not like it........if the drone may be coming from the rear, then I might lean towards a carrier bearing problem......typically with a rear end bearing noise if the sound starts when you are off the throttle and coasting, it is pinion bearings but if the sound starts when you are on the throttle and disappears on coast, it is carrier bearings. If the bearings are just starting to go you may not hear them at slower speeds in lower gears........for your sake I hope it is not that but it sounds like it might be....