This is a rental unit. While driving with the cruise on, set at either 30 or 45 mph (happened multiple times at both settings), traversing over a couple of non-discript rolling hills. After the second hill on the down side the transmission revs to about 4k and accelerates. Hitting the brakes didn't stop the car until about 3-4 hard pumps on the brakes. Pressing the button to turn the cruise off stopped the problem. Very scary. We were able to recreate the problem numerous times. Stopped using the cruise until we turned in the car.