How many hours?? The cummins is a plus, look at the bars and cage, accelerator rolls, and the chopper blades. Run it and it should be smooth with no noises or vibrations. Some check the bottom of the feeder house for wear and the feeder chains. Sometimes the auger pivot may need work - so I would run that in and out. Look at the bottom of the grain bin for rust. The cage will speak the loudest to wear. Radiator should be clean with no dust sticking to it. Ask for service record