These trucks are notorious for need trans replacements for a variety of problems. If you look in classifieds, probably half of the Expo's/Ranger's for sale with automatics say either "new trans" or "needs trans." I agree that it just sounds like yours is worn out. You say you have 240k km, that's 150k miles to myself and my english unit friends - about the time those tranny's go out- actually, you did better than most...!