2018 5.3L Tahoe - 34K miles - Transmission Fluid Temp keeps going 'up' not regulating

[Lbi2000]

Hello, this all started last week when i was coming off highway after towing a boat for about 2 hours (3.5K load) and i noticed my radiator fans were running high, so high i don't recall that. My coolant temp gauge in car showed around 180, engine seemed very hot. My OBDII device that i plugged in showed coolant temp was 145... so i thought for sure i just needed to replace the coolant temp sensor.

So... i replaced my coolant temp sensor, thermostat ( 207F trigger like original had) and i even replaced water pump. Even flushed transmission coolant and did oil change.

MY PROBLEM NOW: i never knew how to show the transmission fluid temperature but now i do. Driving around without towing but with tow feature turned on... i drove about 30 mins on fairly flat/small-hills area.... in 30 mins my transmission temp climbed up ( like about 1 degree per minute it starts to climb! ) up to 208F !!! By the time I got home, another 30 mins later, my transmission fluid temp was 228F !!!!! My coolant temp stayed around 210 never going higher than 214.

Does it sound like my transmission thermometer might be messing with me and i should do that by pass to it ? I mean my transmission coolant ended up running hotter than the engine.

Any advice on if it sounds like the transmission thermostat is the culprit and i should bypass it with the kit ?

 

[Tahoe14]

@NickTransmissions

 

[strutaeng]

Yeah, maybe your transmission thermostat gizmo got stuck closed? I thought that was a common issue on the earlier 6 speeds though. But anything can fail.

 

[NickTransmissions]

Hello, this all started last week when i was coming off highway after towing a boat for about 2 hours (3.5K load) and i noticed my radiator fans were running high, so high i don't recall that. My coolant temp gauge in car showed around 180, engine seemed very hot. My OBDII device that i plugged in showed coolant temp was 145... so i thought for sure i just needed to replace the coolant temp sensor.

So... i replaced my coolant temp sensor, thermostat ( 207F trigger like original had) and i even replaced water pump. Even flushed transmission coolant and did oil change.

MY PROBLEM NOW: i never knew how to show the transmission fluid temperature but now i do. Driving around without towing but with tow feature turned on... i drove about 30 mins on fairly flat/small-hills area.... in 30 mins my transmission temp climbed up ( like about 1 degree per minute it starts to climb! ) up to 208F !!! By the time I got home, another 30 mins later, my transmission fluid temp was 228F !!!!! My coolant temp stayed around 210 never going higher than 214.

Does it sound like my transmission thermometer might be messing with me and i should do that by pass to it ? I mean my transmission coolant ended up running hotter than the engine.

Any advice on if it sounds like the transmission thermostat is the culprit and i should bypass it with the kit ?

Flip the pill or install the Superior Tech delete kit. Keep temps no higher than 185-190. 228 degrees is too high on a reg basis, esp with the POS converter looking for any reason to fail (disregard if you have already upgrade).

 

[SpyShops212]

What if I ran my transmission for a 30 mile trip at 190-195? Am I in trouble in the future. I also changed my first fluid at 69,000 miles on my 10 speed. Most of my miles was highway and no towing. Should I be worried in the future?

 

[Lbi2000]

UPDATE: i installed a transmission cooler and additionally installed the Shift Solutions #STL010 bypass and my tranmission temperature went from climbing up to stupid levels above 200+ to now go only as high as around 143F.

 

[blackelky]

UPDATE: i installed a transmission cooler and additionally installed the Shift Solutions #STL010 bypass and my tranmission temperature went from climbing up to stupid levels above 200+ to now go only as high as around 143F.

You do an oem cooler or aftermarket like trucool derale etc.?

 

[Jonmurphy]

Hello, this all started last week when i was coming off highway after towing a boat for about 2 hours (3.5K load) and i noticed my radiator fans were running high, so high i don't recall that. My coolant temp gauge in car showed around 180, engine seemed very hot. My OBDII device that i plugged in showed coolant temp was 145... so i thought for sure i just needed to replace the coolant temp sensor.

So... i replaced my coolant temp sensor, thermostat ( 207F trigger like original had) and i even replaced water pump. Even flushed transmission coolant and did oil change.

MY PROBLEM NOW: i never knew how to show the transmission fluid temperature but now i do. Driving around without towing but with tow feature turned on... i drove about 30 mins on fairly flat/small-hills area.... in 30 mins my transmission temp climbed up ( like about 1 degree per minute it starts to climb! ) up to 208F !!! By the time I got home, another 30 mins later, my transmission fluid temp was 228F !!!!! My coolant temp stayed around 210 never going higher than 214.

Does it sound like my transmission thermometer might be messing with me and i should do that by pass to it ? I mean my transmission coolant ended up running hotter than the engine.

Any advice on if it sounds like the transmission thermostat is the culprit and i should bypass it with the kit ?

You do an oem cooler or aftermarket like trucool derale etc.?

I've been modifying working on automatic transmissions for many years and I feel 200° is a absolute maximum temperature And a minimum ?,I cant imagine that a ambient over 30° would require a thermostat.. I've said over and over again, Adapter engine oil filter Or 2 , in parallel , On your coolant line.. Converter cluches are very dirt Producing.
All This is will increase your transmission life 3 -4 times ....JonMurphy's law.

 

[B-train]

@Jonmurphy that is an interesting idea. Where do you mount said contraption in an engine bay full of stuff? What size spin on, etc.