Toyota Repair: front end noise, bf goodrich, kelly tires

Question
Hi Mike,
I have a 1999 toyota sienna LE six cylindar with approximately 79,000 miles. The problem with the car started around 58,000 miles. When the speed of the car gets to about 25 miles per hour, a low pitched roar or whirring sound can be heard that seems to be coming from the front end. This constant drone gets louder as the car goes faster. I have put the car in neutral while the car is rolling at between 35 and 45 mph, but the noise does not change a bit.  I had brought the car in to Toyota about 20,000 miles ago, and they said that it was tire noise from the Kelly Navigator tires.  Toyota rotated the tires, cleaned the brakes and changed the transmission fluid as a general maintenance at that time, but the noise did not go away. Recently, at around 76,000 miles, I changed all four tires to BF Goodrich control plus high mileage tires. Even with the new BF Goodrich tires, the noise is exactly the same as it was when I had the Kelly tires. Other than regular maintenance, the car has had no major work except for some steering rack adjustment or replacement that Toyota did at around 20,000 miles to free up minor sticking when I turned the car to the left. I have the Oil changed every 3,000 to 3,700 miles, and have had the transmission changed two or three times over the life of the car. Do you have an idea what might be causing the noise?
Thanks so much.
David

Answer
Noises are tough without actually hearing them.
Educated guess:

Drive on a safe straight road, Shut the engine off while coasting. Noise gone?
That would eliminate engine, power steering etc.
To isolate to one side. Gently swerve left and right and see if the noise changes. If it does then I would suspect a wheel bearing.
The noise will get louder on the side you take weight off. When you swerve right, you take noise off the left side wheel initially.and vise versa.
If the noise gets louder when you take your foot off the gas it would likely be the differential in the trans.
Constant noise, no change at all may be Transmission.
Drive axles by nature dont make noise. Bad CV joints will click or growl only on turns or hard accell.
Mike