In Reply to: Found the cause - This looks like a major issue posted by Kimberly on April 20, 2019 at 11:47:42:
I can't image the tractor would operate properly with one of the arms on the spider missing but who knows. Any chance the differential was replaced and that part was left inside? What is the diameter of the broken piece? If it is the spider the fix probably isn't expensive but it will be some work. There are two sets of used spiders with gears on eBay right now for $65 each.