Have an '02 Tribute 2wd, 3.0 V6, slowing down from highway speed to 45, and then accelerating back up, car seems to buck a little. twice the speedometer has went to 120, then to 0, and then up to actual speed. Was told it may be a "speed sensor in transmission", but cant seem to find such an animal. Anyone have any ideas?Could it be that it is trying to go in and out of overdrive? Also was told by a dealer in town that it was the alternator. Could that be possible? I mean the battery is holding up.