2009 Silverado 3500 HD Duramax LMM overheating

Thanks for the quick responses. The stock front bumper is still in place. This happened when the truck was brand new, and not since. Most of my driving is on flat land with one trip west per year. The temperature lights did not come on. Engine temp was higher than trans. So maybe this is a normal occurrence. As far as speed, I remember moving quite slow passing a semi, which was creeping.

Is the Duramax Forum on this website?