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Need Help Please!!!! I truly appreciate anyone that reads this long post. Hopefully someone can help me figure this out. Bought my 2017 Silverado CrewCab LT Z71 new. For 5 yr & 10 mo. the temp gauge sat at 210 with no issues and no variation. Then, in June 2023 the temp started rising about 10 degrees and would fluctuate from there back to normal. Thermostat was replaced, didn’t resolve the issue. Temp sensor was replaced, didn’t resolve the issue. Truck is well maintained, radiator/coolant flushes done a normal intervals with no issues found. Dealership has checked out this issue 3 times and says it’s operating as normal, temp fluctuation is normal. I have been calling BS on this since June, how is this normal? Almost 6 years with no variance but now it’s normal? So here I am in October, with continued temp issues that are anything but “normal” The temp gauge has progressively increased, the gauge goes up to 245-250 then will drop back down to 210 and fluctuates between 210 - 230/235 as the drive continues. Things to note: I have never had a Check Engine light, adding to the frustration. Coolant level doesn’t change, no leaks whatsoever. This temp issue does not happen when idling. I’ve idled for 20-30 min both from cold and after driving with the issue happening, no fluctuation. I have thought through some other possible issues but then wonder could it be “this” when the issue is not consistent or throwing codes. Are the active shutters not opening / operating correctly, that should throw the check engine light Belt is loose, again should be a more consistent issue with sounds and other functions having issues. Water pump going out, again I think that would cause more consistent issues and would overheat the engine. Fan(s) going out, wouldn’t that be more of an issue when idling vs driving and would be a more consistent issue. Could this be some other sensor, relay, electrical issue. Any help, experience, and/or suggestions you have on this issue are greatly appreciated.

Hey guys, I did the thermal bypass conversion to active by pass on my 2018 8L90. Did a step by step video because I hadn’t seen anybody do an actual full replacement video nor had I seen one on a 8 speed. Trans runs about 45 degrees cooler now. Check it out and let me know what you think. It’s the exact same procedure on 6 speeds just mounts different on the transmission.

Folks with the 159’ trans thermostat, over long drives does your trans temp still climb well over the 160 mark? I drove my 17 Sierra 220 miles today and by the end of the drive it had reached 180’ in 80 degree ambient temps. I would like to think the cooling system is efficient enough to keep it lower..?.. The condenser/trans cooler was replaced a while back, but this issue happened before that. Once I parked and let it idle, it dropped to 165 in 15 minutes. I’m not concerned right now, but I will be when it gets too 100’f out (Alabama weather, yay) and I’m pulling my boat to the beach or my other truck to and from the track on the flatbed. Do y’all think I’m missing something here and I have some issue? Or is this the standard and I need to just add an external cooler? When I first swapped the 159 thermostat( when the new trans was put in) the temps stayed at 145 all the time, but it hasn’t been that way in quite a while. I even pill flipped it and all that did was make it take forever to warm up but to the same effect. Full system fluid change was done about 1k miles ago with oem filter and ac delco dex6 fluid. Trans has around 47k on it. Truck has about 127k on it. Do y’all think I’m missing something here and I have some issue? Partially plugged line? Or is this the standard and I need to just add an external cooler? Any help would be appreciated at this point..

Okay so I broke my foot a last month so my truck has been sitting during the winter. Just recently the check engine light has came on. I used my code reader and is said the thermostat was running cold. And the engine fan automatically comes on and stays on for a little even after I turn the truck off. My question is there a simple fix to this? Or would this require a replacement?

I want to start by saying i understand i am working my truck a tad hard. And I AM going to continue. I just want to protect it as much as possible while doing that. I have a 2014 silverado with the 4.3 v6. 102,000 miles and never a problem. Owned since new. When i haul heavy up gravel roads my tranny gets hot like....220-240. I am a carpenter and pull materials and box trailers. I installed a snow plow this year which is snow moving so not a lot of air moving past radiator. I have hit 250 before. I had the transmission flushed at 50,000 and again at 100,000. But i would like to get my temps down. I am thinking an aftermarket fan? An additional tranny cooler? From what i read the tranny cooler is basically built into the radiator. And because the engine runs so hot you wont get too much cooling ability. Also it dosnt start actively cooling until 190? So i guess i need to adjust my thinking to the trucks 190 and up temperature range. But I am not happy with 230 for hours on end. I dont plow commercially just a few small drive ways. Any technical advice, not just opinions(lol) would help.

Earlier in the week my check engine light came on and I saw the P0700 and P0711 which lead me to Transmission Fluid Sensor issues and people having to replace them. I started monitoring the sensor and noticed it didn't fail like most other people but it takes an awful long time to warm up only peaking at 150F whereas previously it seemed to always be near 200. It took about 45 minutes of driving to get into the 140's and only passed 150F after another hour of driving after that. As I learned the thermostat is only supposed to open up at 192F so I believe mine is stuck open. I will see if the dealer will give this under warranty but I'm curious, anyone do thermostat deletes and regret it? From what I read, the TCM wants 200F or close to it for better shifts and this is why the thermostat is there in the first place. On the other hand, living in a warmer climate where it doesn't usually get below 40-50F, could leaving this thermostat open extend the transmission life?