[boarder_punk]

Most auto trannys use a seperate band internally so that the driver can manually choose gears, thus the 3 2 1 markings on your gear selector. This band generally has the same thickness (although it may have a smaller surface area) of friction material as the normal forward band, and in most trannys is designed for engine braking. Also, when this band is applied it should be holding completely, not slipping, so also not wearing its friction surface; when brakes are applied they slip (unless the wheels are locked up), so they wear more quickly than they would if they didn't slip.