I just recently pulled the top and bottom seives, both rails, shaker pan and finger bar out. I pulled all of this to put in a new shaker pan and was looking at the bushings on each side of the combine. The bushings don't appear to have a lot of wear on them or cracks. How much wear is to much wear on them? My old shaker pan and finger board were cracked so I replaced them, where might I check for other flaws? The rails and sieves have no cracks, but I need the new door that has the spring loaded pins that sit between the spinners and sieves.