Frank there are a few things to look for, the normal engine faults, check for signs of overheating and make sure the coolant looks fresh, main issue is the IRD unit and prop, go backwards on full lock, make sure there is no resistance, this shows the IRD unit has sezied, check for a banging noise on take up of drive, worn rear diff mounts are common place, :-) failing that buy a derfender lol