2014 GMC 1500 Crew, transmission overheating

[NH14GMC]

Hi All, new to this but thought I would throw out a question.  A couple weeks ago my transmission overheated on the highway at 75mph.  I was towing a small uhaul car carrier (empty) going to pick up a car.  I pulled over and let it cool down.  I had the transmission serviced right away and it still runs up to 225-230 degrees if driving any distance.  today when it warmed up, I checked the lines coming out of the transmission and they were barely warm.  Could that thermostat on the side of the transmission be sticking, plugged line somewhere?  Thanks in advance for any feedback or suggestions.  Truck has 117K on it.

[Coachs]

Looking for the same answer 

[Grumpy Bear]

On 9/22/2020 at 2:15 PM, NH14GMC said:

Hi All, new to this but thought I would throw out a question.  A couple weeks ago my transmission overheated on the highway at 75mph.  I was towing a small uhaul car carrier (empty) going to pick up a car.  I pulled over and let it cool down.  I had the transmission serviced right away and it still runs up to 225-230 degrees if driving any distance.  today when it warmed up, I checked the lines coming out of the transmission and they were barely warm.  Could that thermostat on the side of the transmission be sticking, plugged line somewhere?  Thanks in advance for any feedback or suggestions.  Truck has 117K on it.

Yes.

[NH14GMC]

So as a follow up, I replaced the thermal bypass, if that's the technical name for it, on the side of the transmission last week.  (cost me $83.00 inlcuding gasket and 15 minutes of time) SInce doing that, the transmission seems to heat up much slower and when/if it hits 190 degrees, it hasn't gone any higher in the last week of driving and in most cases, drops down to 185-187.

Thanks!

 

Edited September 30, 2020 by NH14GMC

[Grumpy Bear]

Your welcome.

 

Now take you old thermostat and carefully disassemble it taking note of the exact order and orientation of parts. That one at the bottom is the "heat engine" aka 'pill'. Turn it upside down and reassemble in reverse order. You have now made yourself a bypass system that will take 30 to 50 degrees F.  out of the ATF and go along way to increasing transmission life.