I suspected wheel bearings, but just had those check out fine. Tires are about a year old, in very good condition. Thinking somewhere in the drive line but hoping to narrow it down a bit and try any easy fixes before taking it in. Just had the vacuum booster oil leak fixed and that cost quite a bit.
The sound becomes noticeable about about 50 km/hr. It's a whine (not a growl, no clunking), but not super high pitch. I would say not like an electric motor, more like a gear or bearing noise. It's slightly intermittent, but pretty well reliable at highway speeds. It seems to be connected with throttle action but not 100%. I can hear it when I'm steady on the accelerator, and particularly when coming off the accelerator at highway speed. Maybe most pronounced when off the accelerator and coming down a long highway hill (not on the brakes).
As I type this it feels like a wild goose chase, but hey, who knows. Maybe my vague description rings a bell for someone, or if not, once I get it fixed I can post the solution and maybe that helps someone down the road.
Cheers,
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