"transmission hot idle engine" message alert setting

[GMCTom]

2018 GMC Yukon SLT
While taking a 1,000 mile trip to 9k elevation, my GMC Yukon alerted with a "transmission hot idle engine" message. I Let the vehicle cool for about 45 minutes, then resumed driving. The message alerted one more time, and I pulled over and let the vehicle cool for 20 minutes. No more alerts occurred that trip, but there were no more steep uphill legs either.

Question for the forum, what is the "transmission hot idle engine" message set to alert at?
After doing some reading on this forum, I set the dash to display the Transmission Fluid temp. so I could watch it. While the alert has not occurred again, the transmission fluid has reached a max temperature of 260. Trying to understand norms and if I have an underlying transmission issue that I need to look into.

Thanks in advance.

 

[Rygrego]

That's way too hot. I would replace the transmission fluid thermostat with the updated one from a year or two back. It will keep your fluid well below 190 degrees. Temps that high will soon leave you on the side of the road. The fluid in my 2016 SLT never exceeds 180 degrees with the updated thermostat and a Mishimoto trans cooler no matter the temp outside or whether I'm towing.

 

[15burban]

Along with the updated thermostat or just delete it I would replace your trans fluid asap. That fluid got cooked.

 

[Marky Dissod]

the ATF has reached a max temp of 260F.
Trying to understand norms and if I have an underlying transmission issue that I need to look into.

EVERY TIME the ATF hits 248F, it and the ATF filter need to be changed. EVERY TIME.

That's way too hot. I would replace the transmission fluid thermostat with the updated one from a year or two back.
It will keep your fluid well below 190F. Temps that high will soon leave you on the side of the road.

THIS.

 

[Rygrego]

Along with the updated thermostat or just delete it I would replace your trans fluid asap. That fluid got cooked.

I totally agree.

 

[GMCTom]

That's way too hot. I would replace the transmission fluid thermostat with the updated one from a year or two back. It will keep your fluid well below 190 degrees. Temps that high will soon leave you on the side of the road. The fluid in my 2016 SLT never exceeds 180 degrees with the updated thermostat and a Mishimoto trans cooler no matter the temp outside or whether I'm towing.

Thanks for the reply

 

[NickTransmissions]

Thanks for the reply

Drop the pan, inspect for burnt clutch material or any melted rubber material...Id also drop the valve body and replace the seals between the vb assembly and pump + center support as 240+ makes for crispy critters and melted sealing surfaces.

Do a complete flush, get all the old fluid out.

 

[GMCTom]

That's way too hot. I would replace the transmission fluid thermostat with the updated one from a year or two back. It will keep your fluid well below 190 degrees. Temps that high will soon leave you on the side of the road. The fluid in my 2016 SLT never exceeds 180 degrees with the updated thermostat and a Mishimoto trans cooler no matter the temp outside or whether I'm towing.

Thanks Rygrego, and all,
ODB code came back with a failed transmission fluid cooler thermostatic valve.
One valve ($131) and three seals ($10) fixed my issue
& yes I replaced the fluid, filter and pan.

Display now reads between 149 - 182 for Transmission Fluid temp

Thanks for the help on this - you all are great!

 

[Bagherra]

Got a part #?

 

[GMCTom]

GM Valve (Part# - 85585333)
GM Seal (Part# - 85628205)
GM Seal (Part# - 23277649) Needed 2