Yes mine goes away once the engine starts warming up.

Exhaust leak or plugged up converter? That seems to be the only thing left untouched on yours.

 

Just when cold huh? How about the radiator fan clutch, or the bearing for the idler or belt tensioner pulley?

 

The fan clutch was replaced (annoying roaring noise), the tensioner pulley was changedas well- havn't touched the idler pulley yet, but this whistle doesn't sound like a bearing noise. The slightest change of throttle will make it fade in or out while trying to maintain a constant speed. The exhaust system was checked for restriction by removing the forward O2 sensor at the cat and installing a gauge-can't remember exactly what the rading was, but it was within spec. Thanks for you input. What the heck am I missing ?

 

It might not be restricted, but if it has a hole somewhere in it, then the escaping exhaust could make a whistling sound.

 

Just checked the exhaust system front to back, the only spot other than the end of the tailpipe that shows any trace of exhaust is the condensation drain hole at the front end of the muffler

 

My 2001 B2500 is whistling too. It's from the serpentine belt when the temps get really cold out. The colder the more it whistles. I've added belt spray to no avail. So, when I get so money, the belt will be replaced.

 

The belt has been replaced already (2 belts before 60K ?)
It's damn cold here this morning- almost -30. Whistling like a banshee. I'm going to enlist my son's help to try and post a video/sound clip. Can't believe it's this hard to nail down the problem.
So far, no one has commented on the vac gauge readings or the fact that I get allmost 4 MPG better with the overdrive off. The build sheet states axle ratio 3.55 the gears are stock as far as I know and I'm running the stock P245/75 R16 tires. I havn't gotten around to installing a temporary tach yet, but when the road test was done with the scanner hooked up, I was told " everything checks out normal"
My best chance at resolving this issue is to hear from someone who has gone through the same thing and hopefully found a fix.

 

We use to own a 4-cly 1992 Plymouth Acclaim, bought new. After four years, it started to belt whine a great deal. The problem was the alternator pulley became miss aligned. That's the only problem I ever had with that car.

 

I don't mean to but I truly think you're having an issue with one of the pulleys. Just last month there was a loud whistling sound coming from under the hood of my Expedition. You would've sworn up and down that it was a vacuum leak but it wasn't. It turned out to be one of the idler pulleys wasn't turning. That's right, frozen solid, but only when cold.

The belt was fine and was sliding over it, smooth as silk. As soon as the engine warmed up and got some heat into the pulley's bearing, it would start turning and the noise would go away.

 

I just finished checking idler and tensioner pulleys- both hot and cold. Both bearings appear to be O.K. I ruled out the A/C clutch bearing as the noise occurs with or without using the defroster ( compressor cycles on defrost). Rule out the water pump bearing (new pump). Hot or cold, the alternator and power steering pump feel O.K.
I've driven this van with this noise for 48,000 KM. If a bearing was making the noise, don't you think it would have completely packed it in by now ?