chances are that if you do not feel the engine brake, then the auto trans has already downshifted into third itself.

I would think heading for a red light you would not be in 4th. or 5th., unless you did it on purpose.

This would be more noticeable while slowing down for a exit from highway speeds......then the trans should be in high gear.....and you would then feel the (premature IMHO) downshift if you shifted from D to 3.

Anyhow.....the kenitic energy(motion of the car)has to go some place when you try to slow down,....so insted of it turning into heat on your brake pads/rotors....it will go into heat inside your auto trans. I think it would cost much less money to replace pads/rotors, than it would to replace a auto trans.

just my 2¢ on the whole thing

BTW: I would manually "downshift" a auto trans only if I was on a long down hill grade, and did not want to overstress the brakes....but it woud be to keep the car from speeding up too much....not to slow it down after it sped up.