This might sound odd to you. But noise travels in mysterious ways.
If you can't find any propblems in the front, I'd suggest you check your rear wheel bearings.
Since your noise seems to be coming from the front left, my guess is that it could be coming from your right rear.
Again I know that sounds screwy, but I've dealt with this issue several times on different trucks and rear wheel drive cars over the years.
If you catch it before the axel shaft is damaged you can use standard replacement bearings and seals. But if the shaft is damaged ask for a bearing repair kit. The kit moves the bearing race to an area of the axel with out damage, if also includes the seal.
Replacing the rear bearings isn't that difficult. But if you don't already have one, I'd suggest renting a slide hammer kit. It will make getting the bearing race out of the axel housing much easier.