Check out the service records and make sure the major stuff was taken care of, ie, diff fluid, plugs, coolant, timing belt(due at 105k),trans fluid etc. Find out if major items have been replaced (clutch, tranny, exhaust, etc.) If everything is cool, I recommend letting a dealer do an inspection. If your close, have Kelly at Mastro take a look at. Many AWD owners may just change out one or two tires at a time. This can kill the differentials, even if there is 2/10's difference in treadwear between tires. Check to see if he has receipts on tires and when they were changed. Hope this helps.