2019 Yukon/Transmission fluid temp problems

[marayabarr]

Good afternoon,
I’m trying to get to the bottom of my problem and can’t seem to get it right. A little back story, bought a used 2019 Yukon back in march of 2023. Everything seem right no issues whatsoever. Fast forward to January of 2024 on the way back from Wisconsin to Florida where I reside the transmission took a sh*t in Tennessee. Check engine light pop up and took it to a dealer to confirm the diagnostics. They came back and told of that it was a transmission issue and that it will need a new one. Had the vehicle transported to Florida and a dealership down here did the replacement. Vehicle drove fine after new transmission installation. A few days later I noticed that the transmission fluid temp was kind of high around 260-270. So I took it back to the dealership to see if they can tell me what was going on. They said it was normal, which I didn’t think it was. So I kept driving it but the temperature never got below the 240 mark. Took it back to the dealership so they can properly do a diagnostic and all they can say it was that it was all normal and there was no issue. During my research I was able to come across some info that said I should replace the thermostat which I did but it didn’t change anything. I also changed the thermo bypass valve in the transmission cooler lines and didn’t solve the problem. Today I changed the radiator thinking that maybe the transmission cooler itself that’s inside the radiator might be bad. But that didn’t change anything fluid still reaching temps of 270 in normal driving conditions. If there’s anyone out there that can point me in the right direction or maybe have been through this please let me know. I love the car but I’m dumping money and the problem still not fixed. Thanks for taking your time. I hope I can hear some good news.

 

[Big Mama]

Sounds way too hot. It came with a warranty, right? @NickTransmissions may have some other things to check.

 

[viven44]

Do you know if they replaced the torque converter when they installed the new transmission ?

How many miles on the Yukon currently and how many when you bought it?

 

[NickTransmissions]

Good afternoon,
I’m trying to get to the bottom of my problem and can’t seem to get it right. A little back story, bought a used 2019 Yukon back in march of 2023. Everything seem right no issues whatsoever. Fast forward to January of 2024 on the way back from Wisconsin to Florida where I reside the transmission took a sh*t in Tennessee. Check engine light pop up and took it to a dealer to confirm the diagnostics. They came back and told of that it was a transmission issue and that it will need a new one. Had the vehicle transported to Florida and a dealership down here did the replacement. Vehicle drove fine after new transmission installation. A few days later I noticed that the transmission fluid temp was kind of high around 260-270. So I took it back to the dealership to see if they can tell me what was going on. They said it was normal, which I didn’t think it was. So I kept driving it but the temperature never got below the 240 mark. Took it back to the dealership so they can properly do a diagnostic and all they can say it was that it was all normal and there was no issue. During my research I was able to come across some info that said I should replace the thermostat which I did but it didn’t change anything. I also changed the thermo bypass valve in the transmission cooler lines and didn’t solve the problem. Today I changed the radiator thinking that maybe the transmission cooler itself that’s inside the radiator might be bad. But that didn’t change anything fluid still reaching temps of 270 in normal driving conditions. If there’s anyone out there that can point me in the right direction or maybe have been through this please let me know. I love the car but I’m dumping money and the problem still not fixed. Thanks for taking your time. I hope I can hear some good news.

See if you can take an independent temp reading at/on the pan with an IR thermometer once it gets to op temp. If you're really running around 250+ all the time, you will be yanking it back out soon. The torque converter accounts for the majority of the heat built up inside an auto trans so its possible the tc is slipping when it should be locked.

Drive it to an independent trans shop, have the tech take it out with a bidirectional scan tool showing live transmission and torque converter data displayed. If the tcc slip speed is above 10 at or near max duty cycle, it's slipping and that's the where the excess heat is coming from. Also, flip the pill in the TBV if you havent already - takes about 15-20 min at most.