Re gear 1st gen Tundra 8.4 Rear dif

First gen 8.4 re-gear Tundra rear dif, also in T100. Complicated design and too small. The Tundra should have had larger front & rear axles considering this was supposed to be a T150. I have replaced the third member every 90,000 miles and currently have 340,000 miles on the truck. Spider gears fail every time and no one knows why...