[no_roads]

I work part time in an auto shop and I've seen people come in that say that they are trying to save gas so they will actually shift the vehicle into neutral while coasting down a hill and then shift it back into drive later thus resulting in burning up the tranny alot faster. The reason it burns the tranny up faster is because of the synchro's in it for each gear and it's basically easier to put it like this, you wouldn't put a car into first gear(on a manual/stick shift) at 60 mph would you? Which is exactly what you are doing when you have an automatic, your tansmission thinks it is starting from a stop so naturally it uses first gear then it has to react extremely quickly because it pretty much was just slapped in the face and told to do something. The basic answer if you for some reason didn't understand my explanation is that it is really, really bad to do that and it really doesn't save you that much gas/fuel to constitute paying to either buy a new tranny or rebuild the one that you have.