My second Explorer, first one did not have any issues. Bought it used with 30000 miles on it. Driveshaft was vibrating, dealer replaced, worked OK to 40000 miles when check transmission light came on. Dealer spent two weeks repairing, cost was covered by extended warranty. After the repair rear differential began to make noise. Also shifting was not as smooth as it used to be. Have decided to trade it in.
Very comfortable SUV on the road, lots of room with 3rd row seat.
Reliability; these kind of issues should not appear before 100k miles.