Drivetrain squeak

[fintubi]

Configuration: ERA slabside with Jag rear assembly

Symptom: repeating squeak in time with wheel rotation.

Traits:
- only happens after car has been driven 10+ miles at decent speed
- gets louder/harsher fairly quickly over a ~5min period
- sometimes goes away with further driving
- seems to diminish under moderate to hard acceleration, is loudest at light throttle or deceleration
- still occurs when coasting with transmission in neutral

None of the above rules out a front end issue, but it feels like the sound is coming from the rear half of the car and the sensitivity to power/coasting/decel makes me think it's somewhere in the drivetrain.

Any ideas? Conforms roughly to the symptoms of a wheel bearing issue on a regular car, but the Jag rear is more complex. What should I check or lube?

When it's at its worst, it sounds so obvious I feel like I could jack up the car and find it by hand; but of course it never happens when I have that opportunity.

Bill