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Discussion Starter #1
I drove for 400 miles yesterday, with ambient temps in the low 50's, usually lower though, and the temperature gauge never got to the 1st tick mark. I was pulling a 2K empty trailer also. Good thing it wasn't cold, the heater output was minimal. Sound like a bad thermostat or 2? How hard are they to change? Just hit 100K miles.
 

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My guess is that your temp gauge is faulty; this just happened to me (see my thread about possible overheating). If so, you would have to change out the entire cluster. Although possible, both thermostats would have to stick open, an unlikely scenario. In my case the dealer was able to scan the vehicle while running and determine the sender was sensing 180 degrees, while the gauge did not register at all.
 

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Discussion Starter #3
Today, high around 57, and I put the upper grill cover on. The gauge registered about as high as it normally does, the same as it has since day one. Take it off, the temp goes back down. So it does not appear to be the gauge. The odds of both sticking open would indeed be slim, but would just one open do it? Why 2? Any other possibilities?
 

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As others have said before, the gauge is not necessarily that accurate, so that is one thing to keep in mind. There is another thread, if you do a search for "thermostat," that shows a diagram and some tips on replacement. It looks straighforward. In my case, the gauge malfunctioned intermittently, which made a diagnosis difficult. The dealer checked the gauge and all was OK the first time. Finally, the gauge failed to register at all, and the dealer scanned it while running and confirmed the bad gauge. It took a couple days to get a new cluster ordered and in the meantime I drove my truck and the gauge seemed fine. Since replacement of the cluster, no further problems.
 

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Discussion Starter #5
I did a search under "thermostat replacement" and found nothing of value. I'll try just "thermostat".
 

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My truck has been doing the same thing as yours. A couple of days ago the engine chatter got very loud, idle rpm increased and the trans starting downshifting very hard. Took to dealer and found that ecm had set code P0128. This code is set when engine temp is running to low. Dealer said I need new thermostats, which they had to order. When the tech cleared the code the engine went back to normal but the trans ecm had to be reflashed to correct the shifting problem.
 

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Discussion Starter #7
Well, that's interesting. Mine is a little louder, but I have no codes set.
 
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