Lately when driving 60mph or so the RPM's will suddenly spike and the car will jerk. It usually does this once or twice then stops for a couple minutes. About a year ago I had the tranny rebuilt with new 4th gear hub, solenoid, shift kit etc. I replaced the plugs, wires, and fuel filter as a place to start. Car has 113,000 miles. Any idea's on where to start would be appreciated.