Venture :: 2000 - Grinding / Buzzing Sound When Traveling Above 25 MPH

2000 Venture short wheelbase 122k miles. Original owner from brand new. Has had fuel pump replaced at 40K, intake manifold replaced and full trans (torque converter inclusive) flush, plugs and wires at 75K. (2005) All fluids checked regularly.

Recent problem. Noticed a "grinding/buzzing" sound when traveling above 25 mph. Sound is commensurate with veh speed (not engine speed). If I turn the wheel ever so slightly to the right, the sound "deepens"/gets louder), and I can feel the buzzing in the steering wheel. When I release from turning right, or turn left, the buzzing greatly decreases (though I still hear it), and I can no longer feel it in the steering wheel. I only feel it when I turn the wheel to the right, even just a few degrees.

My thoughts on the culprit (in no particular order): Wheel bearing, Transaxle/final drive (differential). ???????

Wheel bearings: No work done on front wheels/hubs. I did rotors and brake pads in April 2009 (115K). Visual inspection of all of the under car and front end. Nothing appeared out of the ordinary.

Transaxle/Diffierential: Who knows? I have had other vehicles with a normal differential/rear end, that had a bad bearing and I could usually tell which side, just by driving/turning Usually it was an outer bearing (wheel), not an axle bearing (diff).

Observations:

1..Periodically over the last 2-3 years or so, I have had to add about a 8-12 oz of coolant to the overflow every 8 mos or so. I don't know where it goes. I presume it is evaporating somewhere or VERY slowly leaking. Nothing external that can be visually noticed.

2.. Last week I checked the trans fluid. Was off the stick. Had to add 3 qts Dexron VI to bring it to full mark on stick. First two qts. barely registered on the stick. Prior to that last check was at 118k (5 k ago) and June of 2009. My written notes at the time mention "Normal. Didn't smell or look burnt, and no particulate matter in the fluid". Has been a week and the fluid level is still holding fine. Where did the 3 quarts go ???

3.. Opened radiator cap. No sludge or "strawberry milkshake" evidence of trans fluid. Looks fairly clear and orange. About what I would expect for a veh of this age and mileage. All lines to and from trans and radiator look ok. No evidence of leaking ANYWHERE.

4.. Runs an normal temps throughout the year

5.. Shifts fine with no slipping, clunking, grinding (during shifting).

6.. Overall vehicle runs, shifts, handles, and stops well.

7.. Every few weeks the ABS light comes on and then goes out after the next start.

If it's a wheel bearing (and I am leaning that way) How can I determine which side I need to replace? If I turn right, I "load" the left one. Noise gets louder. If I turn left, I "load" the right one. Given the above symptoms should I presume the left one?