I have this 98 3.1 Lumina, with this kinda "wobbling" sound, more like the sound coming from a washing machine in the spin cycle without any clothes in it, but muffled. I've changed both my brake drums and brakes shoes, thinking they might be the problem, but it's still there, comes and goes when I go up or down inclines, braking and just straight driving. I'm not sure if it's the wheel bearing or something else entirely. What do you all think?

try rotating the rear tires to the front. If the noise moves with them, it could be a bent rim, out of balance tire, or cupped tread from worn struts/bad alignment. If the noise stays, it's most likely a bad hub bearing.