2009 Silverado 3500 HD Duramax LMM overheating

If you didn’t get some sort of warning light you didn’t overheat.

Unless you are a huge fanboy of your truck manufacturer, you’ll notice an increase in temps when you are pulling in extremes. Somehow the guys with the name of their favorite brand in their screen name or posted boldly in their signature avoid it. ??

Good luck diagnosing an issue that happened once 10 years ago and never since.
There's nothing wrong with your truck if it hasn't overheated the last 10 years.
And since it was brand new then, there was probably nothing wrong with it then either.

Hard to believe the fan clutch has been out that long, but have you heard the cooling fan lock up?
If you were going slow and didn't have as much airflow and the right conditions, I could see it getting hot.

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?

I've had the same engine/tranny in a 2009 2500 and a 2013 3500 dually. Does your fan turn on? I'll see my temp needle start to rise on a hill then the fan turns on and the temp goes back down to normal. You'll hear the fan kick in.

I'd take it to the dealer and have them check things out.

I'd suggest you be a little more specific about "overheat". Did the engine temp or transmission temp lights go on?

What did the temps read? I've seen my truck get to 230* in both transmission and engine temp on a hot (relatively) day running that route. Also makes a difference if you are able to run straight up, or if you are slowed down by traffic.

You can also go to the DURAMAX FORUM and pose your question in the LMM group; lotsa info there on that particular issue...

Do you have a front aftermarket bumper blocking air getting to the engine? If EGT's are getting high as well, when was the last time you checked for boost leaks?