Transmission fluid temp problems

marayabarr · September 28, 2024

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.

CamGTP · September 29, 2024

It's for sure not normal at all. I'd be going to a different dealership. That transmission will not last long at those temps. It's going to cook the fluid in a very short time frame and cook the seals on the inside of the transmission.

Any transmission tech that is worth a damn will know that seem fluid temps above 220-230 for long period of time will slowly ruin the transmission. There is no way in my eyes that GM can say that seeing 240-270 degrees temps is completely normal operation.

newdude · September 30, 2024

On 9/28/2024 at 7:38 PM, marayabarr said:

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.

Dealer should have replaced the transmission cooler aka the combi cooler (condenser and transmission cooler assembly) as its probably filled with metal from the transmission failing.

The dealer should have already added the lower temperature bypass valve when the job was done so I'd check your receipts for that.

Otherwise, stop driving it before you toast your transmission.

Edited September 30, 2024 by newdude