[cooperino]

I would start by taking a look under tractor. Are all the lift pins good? If any linkage is missing or bent that would cause a problem. If all looks good. check the height of the deck on a flat surface in the driveway. If one side of the deck is higher than the other this will cause scalping and uneven cut. If all your hardware is good and deck is level look at blades next. Also check your spindles for excessive play .