Overdrive noises?

I've used this forum considerably lately, and with much luck,
so I figured I'd try all you experts first on this as well:
I'm detecting a sound I can only describe as a "warble"
or some kind of drone, from the middle of the car, or the tranny.
I think it only happens in overdrive, as it's not there at any
speed in 3rd gear, and goes away when in Neutral. So around
50-55mph, when just cruising. Any ideas? I just had the AWD clutch plates
fixed, and haven't had AWD for awhile...if that helps. TIA!
Yes, I am due for new tires. And no, it's not a wheel bearing.
(Rebuilt tranny with 43K)

[Earthworm]

I'd be inclined to think the U-joints on the driveshaft are worn out.

Originally Posted by Earthworm

I'd be inclined to think the U-joints on the driveshaft are worn out.

Yes, especially since now that it is spinning again...I hear the noise.
Or maybe a slightly bent driveshaft? Are the u-joints special to
this car in any way? Subaru tends to charge dearly.

[Earthworm]

You got it!

The u-joints are built to be non-replacable. Subaru wants you to replace the entire driveshaft. I'm sure some people have found ways around this. We've done this on our Justy.