99 Jimmy SLS 4x4 4.3 v6 vortec - 119k

I totally love this truck, why I don't know. All it does is drain my wallet.

I've replaced so much on this truck, it's pretty brand new in repairville. New: oil cooler lines, rear end, u joints, 4 axles, upper/lower ball joints, injectors, water pump, left & right front hubs, brakes, rotors, 4wd vacuum sensor, heater core, and the normal preventative maintenance as recommended.

Recently, it has been humming very loud from the front end. There is no change in the RPM's, no change in the way it feels on the road. The only change is the fact it hums, and seems to go: "woop woop" when I turn the corners from the engine. So, a week ago I the tension pulley replaced as it was shot. And I replaced the idler pulley and belt for good measure. The sound is still there. The crank pulley seems to be out of round, and kinda matches the "woop woop" sound I am hearing. Replacing these 3 things seemed to take the sound down some.

Another thing, my dash panel for the 4x4 went out a couple of months ago, and before it went out, my "service 4wd" light was coming on & going off intermittently. When I took it in to pull codes off, the light would go off when I turned off the truck, and would only come back on over 40 mph. Eventually the light just stopped coming on, and dash panel went out.

But, my main concern is this noise. Anyone have any ideas?