Deere sells a repair kit/ update kit to reinforce the front legs and other weak areas of the grain tank. I did it on an 03 9750 sts at 1000 hrs. Crops included corn, wheat, barley, mustard, canola, flax, & soybeans.
We had the same problem on our 01 9650sts at around 500 hours. The kicker is, we dont have a hopper extension on it and dont race the combine full across the field. Yet, we still had cracks popping up everywhere. Thanks deere for building a poorly built grain tank. We did get it fixed with John Deere's kit. But even now at 1100 hours, another round of cracks is developing in other areas of the hopper. Its not only limited to the hopper tank, but some cracks are developing as well along the rotor cages near the back beater area.
drewski The part numbers are AH213978 and there is a uloading auger kit that is AH208662, this is in solution number 62757, it says it comes with instructions, there are pictures that are in the solution that will help you.