My 2004 2500 Duramax overheats going up 5% or better grades pulling a fully loaded 10,000 5th wheel. Anything less of a grade no problem. Once it starts to get warm it goes to hot fast. My local dealer has tested everything they can. No answers. Its all stock. Runs great other wise. Help?:help:

This needs to go in the LLY section.. I will see about having it moved.. Thanks