My 1999 Ford Explorer Sport, V6, Automatic with 70,000 Miles is having some problems. When the car shifts into second gear there is a pause for about a second, and the engine will quickly rev-up, jerks, and then it finally shifts. It does not happen all the time and just started about 3-4 days ago. Im worried it may be something with the transmission but i know nothing about transmissions. Any help is appreciated.