08 yukon xl

[Patricktommy96]

Hello, I recently purchased a 2008 yukon xl 5.3 with a tow package, after a couple of weeks using it I noticed on the driver information screen that my transmission temp was running at 200 degrees Fahrenheit.
The next week I was going on a trip with my travel trailer and I noticed the transmission temp was getting really high 200-235 didn’t get higher because I stopped to let it cool down.
The following week I installed an aftermarket transmission cooler because it was not equipped with one.

The transmission cooler has helped to keep it down for not towing it’s in the 160-180 range. But I just towed again just the other day and the temp was reaching 220-235.

Was thinking of installing a cooler fan for the transmission cooler. Any ideas?

 

[Big Mama]

Do you know if/when the trans was serviced? Did you check the fluid level and smell before/after adding cooler? You shouldn’t need a fan. How heavy is the trailer?

 

[Patricktommy96]

Do you know if/when the trans was serviced? Did you check the fluid level and smell before/after adding cooler? You shouldn’t need a fan. How heavy is the trailer?

I just bought it so no I don’t know when it was last serviced.
When I installed the transmission cooler the fluid wasn’t a dark red color it was a lighter red. The smell wasn’t burnt. Also the trailer weighs 5,000LBS

 

[Big Mama]

With the temp climbing while towing it sounds something is interfering with flow or some slipping is happening. I had a GM truck that did the same thing. Daily driving was perfect but I towed once and it got so hot the fluid came out of the vent. I had to stop every hour or so to let it cool. I’m not a trans expert so maybe one will chime in. Have you looked for any TSB on your truck? Look on line with your VIN to see if it’s been reported and it may say what to do next. Sorry I’m not more helpful.

 

[swathdiver]

Hello, I recently purchased a 2008 yukon xl 5.3 with a tow package, after a couple of weeks using it I noticed on the driver information screen that my transmission temp was running at 200 degrees Fahrenheit.
The next week I was going on a trip with my travel trailer and I noticed the transmission temp was getting really high 200-235 didn’t get higher because I stopped to let it cool down.
The following week I installed an aftermarket transmission cooler because it was not equipped with one.

The transmission cooler has helped to keep it down for not towing it’s in the 160-180 range. But I just towed again just the other day and the temp was reaching 220-235.

Was thinking of installing a cooler fan for the transmission cooler. Any ideas?

Your truck uses Dexron VI which flashes at 401 degrees. The 4L65s normal operating temperature is 180-200 degrees which is the HOT section on the dipstick. In order for the Service Clean Procedure to work, the temperature must be between 158-230 degrees. This is also called its normal operating temperature range. P0218 will set if the temperature is 277 degrees or greater for more than 60 seconds.

Bill, @intheburbs has a lot of experience towing with the 4-speeds and can tell you what's normal and what's not and when to change the fluid.