A LC newby (as in 3 days), but very enthused. '02 17K miles (yes!) w/original tires. Spare had previously NOT been rotated in--new with nubs. I decided to rotate the full tread tire in, putting it on left rear. Tread depth difference between 'used' and 'new' tire couldn't be more than a 16th" maybe 32nd? Could a slight tire tread variation cause a problem with the all-wheel drive system? Thanks!