2020 L8T 2500 Transmission Temperature Reaches 230 while towing

allycat75 · September 8

Hello all,

I have a 2020 Silverado 2500 6.4 gas burner. This past weekend while towing our 7500 lbs camper the transmission temperature reached 230 degrees. The tempature outside was around 75 degrees. The road was pretty steep and curvy so I was driving at low speeds, around 35-40 mph. From what I have read online the normal tempature range goes up to 220 degrees and 240 is when you start seeing problems with the fluid degrading. For all of you gearheads is 230 degrees acceptable? When should I start to worry and give it a chance to cool down? and then is, sitting still, idling the best action to take?

Thank you so much for your insight,

Ivy

CamGTP · September 9

I have watched many video's over the years of people reviewing these heavy duty truck and doing heavy tow testing in the mountains and up rural passes. Every single truck these test being it from Ford, Chevy or Dodge all see very high transmission temps when used extended periods of steep grades and more so at slower speeds.

So to me the temps you are seeing fall right in line with all the stuff they have seen with their testing. The temps aren't ideal and the fluid can more than handle that temp. I would only be super worried if you saw temps above 245-250 but at that point the trucks usually end up going into limp mode to save themselves.

The life of the fluid above 200 degrees goes down but it's still going to have life for 20-40k miles compared to life at 75-100k miles if the temps stayed between 150-190 all the time. But things inside the transmission can be cooked if the temps are always 220+, like seals, rubber o-rings, wiring or connectors for the valve body. They just become more brittle over time.

I'm sure your temps smoothed back out once you stopped pulling the grade and got more airflow through the grille. And yes, idling the engine is usually best to bring temps down or get out on the open road with more airflow. The only way to really lower the temps all the time would be install an external transmission cooler to try and bring the temps down by 20-30 degrees.

Wxman · September 9

Allycat75

Two things.

One I agree with CamGTP that you aren't likely hurting the trans in that situation. I have even read the transmission can take temps up to 260, but I too would be concerned about the fluid at that temp.

Two, has your truck have the cooler transmission thermostat installed? It won't keep it cooler when it is maxed out, but if you start a little cooler it takes that much longer to get to temps that are worrisome. You can visually tell if you have the cooler thermostat or not.

I had TSB 21-NA-199 1..3 (nhtsa.gov) accomplished on my 2020. Later builds had the cooler thermostat from factory.

allycat75 · September 9

Thank you so much for your responses. It does make me feel a little better about the 230 temps. And yes it only reached that high for a few minutes. In fact I pulled over because I was afraid of causing damage. I am unsure if I have a transmission cooler. Looks like it may be just what I need to make it run a little cooler. I will definitely look into that.

Another JR · September 9

Often you can reduce your transmission temperature in a part-power climb by downshifting to increase engine speed, which increases water pump speed and flow. This increased flow allows the transmission cooler to reject more heat into the engine coolant. Doing a 35-40 mph climb due to a winding road with a 7500 lbs trailer, you probably did not need max power so your transmission was in 4th much of the time with your rpms at 1700-1800. If you are in that situation again and don’t like the transmission temperature, use L to limit the transmission to 3rd gear to keep the rpms higher at around 2400 and the temperature should come down some.

Edited September 9 by Another JR