02 taurus tranny ?

I just got a 02 Taurus SE with 37 K on it. i have the 155 hp motor, when flooring it and letting the rpm's rev up, this weird thing happens and the car like stops accelerating for a split second and then starts again, real fast... and it does it at a different RPM in every gear after 1st... i dont know if its slipping or what... but its weird it makes the whole car jerk when it does it... does anyone know whats up?