Driving impression: Case IH STX 500 Quadtrac Out on the track Once Challenger had come out with a 500hp+ crawler, it was only a matter of time before Case IH followed suit. In 2005 we took a drive on the STX 500 Quadtrac, a rubber-tracked tractor that puts out 373kW/500hp (ISO) at rated engine speed and is capable of a whopping maximum output of 410kW/550hp