Check the flex coupling on the rear driveshaft (its the rubber thing that connects the drive shaft to the rear diff) and check the fron driveshaft. If you go to rock auto and get the precision u-joints (you will need 3) and the centering bearing you can re-build it yourself if you are handy or let a driveshaft company do it. Trust me the $75 or so dollars for the parts are worth not getting a hole knocked in your transmission it and when one of the u-joints or centering bearing fails. Other than that I'd say it could be a wheel hub. is it coming from a particular side, and if so is it from the front or rear. i.e. if it is coming from the front right, the front right hub/wheel bearings are bad. Let us know what you find.

 

The noise comes from the front only, no particular side, at least that I can tell.

 

At least you have eliminated the cheap fix, and the fluids needed service at some point anyway. $70 was well spent. Does noise happen when you are parked and raise engine to that speed (something turned by serpantine belt)? If you get up to 45 mph on an empty road, slip into "N", does noise continue (tranny vs rest of drive train)? Tranny fluids and filter next? When driving at noise speed, shift car left / right to increase load on front CVs, any change in noise to indicate one side or the other? Rough tire tread? Jack up front wheels and rotate by hand, shake/wiggle to test for any play in bearings. Hub bearing pricey on D2. see http://www.roversnorth.com/store/p-1...covery-ii.aspx

Probably not CVs themselves, normally you would have notice clicks, etc., while turning - see http://www.roversnorth.com/store/p-1...covery-ii.aspx

If it is on the front axle, there are not a lot of parts there, and many are more than a tank of gas. See http://www.roversnorth.com/store/c-413-drivetrain.aspx

BTW - I'm not advocating purchase of parts from this supplier or any other, but I do like the exploded diagrams they have. And certainly looking at their prices it gives you a starting point. As an example see http://www.roversnorth.com/store/p-3...sensor-v8.aspx - more than some D1 owners paid for their whole truck....

 

It only does it while accelerating and cruising. When I let off, the sound goes away, but will return a bit while braking. The noise is not present at all in neutral while coasting and stopping.

 

Alternator whine maybe. ? check your alternator ground strap

 

If it were the alternator, wouldn't it whine in neutral too? The whine is not present while idling or reving the engine in neutral. It will present itself when the speed of the car is in excess of 30mph while accelerating and cruising. It will go away when you let off the gas, but then come back when braking. If I put it in neutral while braking to a stop, the sound is not present. I'm almost convinced it is the differential, but I guess I won't know until I get it on Jacks and listen to it. It could be the torque converter too, but the sound seems like it is coming much further forward and centered.

 

Try at the noise speed or just below it to turn the truck one side or the other, to see if shifting load on wheel bearings plays any part.

 

The sound is constant no matter how hard you turn in either direction. The sound is also the same in hi and lo range and is speed related.

 

OK - if you have a locking CDL, you could drop front drive shaft. If noise went away, rest of power train is clear. Like your theory, the "load" on the front diff brings on the noise....

 

Not necessarily. I have had instances of serious alternator whine with the vehicle drive and drive only. We actually have a DTB on it. I just gave you an option. thas all.