I had the same issue with a 3/4T 4WD truck I own. Odd tire wear. Took it in to have an alignment and it all checked out good. The tires were still wearing funny. I took it in to have them rotated figuring this was the nature of the beast and I would just have to live with it. When they jacked it up, the lower ball joint was bad… Really bad. This was the same shop that did the alignment. The alignment checked out on the machine but was thrown off as soon as it was back on the ground. So, my suggestion: check (or have checked)and replace your ball joints as necessary…