WOOHOOO!!!
The humming is history! It was the differential.
Picked up my truck tonight after the front diff was replaced and the humming, "wu wu wu wu" is gone.
There is a "slight" buzz through the steering wheel and faint hum on coarse pavement, but I think its probably normal. Its been so long that I've had the constant buzz/hum that I forget what the truck should really feel like.
But I'm very happy right now. I won't pop any corks just yet until I've driven it for a few days.
If you have this problem, you may want to have the dealer look very closely at the front differential and have it replaced. My case is on file with Toyota Canada and other dealers can access it I believe.
Here's what is on the invoice: (click to enlarge)
