Our 15-year old Kitchenaid mixer is a beast and we work it hard. During our last batch of bagel dough, the paddle started skipping. After popping the top and removing the transmission cover, a brief inspection revealed that the worm drive had worn and began skipping. I ordered a new gear and bearings; the old bearings actually looked OK, but I figured I was in there anyway. Video instruction provided by AppliancePartsPros.com was great. The repair was straightforward; the most painstaking part was cleaning out the old grease. One tip, while all the screws work with a Phillips head, having a square head screwdriver or driver bit works even better. Our mixer part number was KP26M1XMR...It didn't have a 4 or 5 suffix like those offered in the diagram but the parts worked just fine.