2000 GMC Sierra 4WD Both front end tires badly wearing on the outside edge. Had truck aligned twice then took to mechanic who thought it was the inner tie rods. Replaced those and still having the same problem. When turning the truck to the left the right tire pushes or binds, vice versa when turning to the right. Any suggestions on what the problem might be??

I would have it alined someplace else. This is called camber.