i would think a tire wearing just on the outside would have to be the tire itself or the spindle.I would think if the axle alignment was affecting it the opposite tire would have some type of wear also.Pull the tire in question and swap it with the spare and see what happens,you could also use chalk and mark a line across the tread and drive a few miles and check the wear from the chalk to see how the tire is making contact with the pavement.
06 2500 Duramax. Air lift 5000 air bags,Equalizer WDH, EFI live,fass fuel system,4" straight pipe
2015 Jayco Eagle Premier 314BHDS
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