Mother in laws 21 expedition was bought used with 60,000 miles. It has about 75,000 now. I know the dealer says 150,000 but they like to sell rebuilt transmissions. Some say change the filter and fluid in the pan and don't flush. (I wouldn't flush this high mileage trans anyway). Then change the fluid in the pan after another 10,000 miles. One Ford tech I listened to said to put synthetic Amsoil ulv in instead of Ford ulv. I just need a little information from those who have dealt with 10r/80 transmission.