Hello and help!

Above 70mph I can start to hear a whimpering noise which seems to be coming from transmission line. And it has been getting worse during last 20.000mil. It's gone when accelerating or drivind normally, but when taking pedal up this there. And I can partly feel it on steering wheel, and elsewhere also I think. Can it be something from 4 wheel drive parts? An ideas?

(this one has 75,000mil on it)