My Ford explorer is moving slowly when gas is pressed hard. I have replaced transmission fluid and filter. It goes into reverse neutral overdrive drive 1st and 2nd fine and jerks like any vehicle normally does when put into gear, but when gas is pressed it moves slowly but engine revs high and makes a humming sound like something is spinning around very fast. rear drive axle is fine power doesn't seem to make it into/past the transmission to the drive axle. Any Suggestions besides you need a new/re-built transmission? The car has 145k miles and started doing this out of nowhere while driving down the highway it made no sounds when it started didn't really do anything besides stopped going. Thanks guys.