Transmission Temperature

20Silverado11 · April 13, 2011

Let me start by saying "Yes, I've read my manual." Now that I've eliminated this item from the discussion, let's move on. My new Silverado 1500 has a display in the Driver's Information Center labeled "Transmission Temp". As I drive my truck, the number goes up and down, obviously in response to varying load on the transmission, changes in speed (air flowing over the cooler), etc. Largely, I've observed that the transmission temperature settles in at about 90 degrees F or so above ambient, once the truck reaches operating temperature. So far, we're probably on the same page.

My question is on the topics of what is a normal operating temperature and, more importantly, what is too hot? Neither the owner's manual, nor the Silverado trailering guide make any mention of these numbers, so I'm in the dark as to the purpose of the gauge (or digital indicator) without any point of reference. Apparently, if the transmission gets too hot, the DIC will alert you, but how can I determine if I'm approaching the danger zone while towing this summer? If I were aware of impending warnings (vs. a simple idiot light), I could take appropriate measures - like pulling over at a safe location. But, near as i can determine, without any idea of what is normal or high, I just drive until the truck complains...right?

Please help - I like to have more information than less. Thanks!

Marc

[email protected] · April 13, 2011

Here's what the gauge looks like my 2001 2500hd, and you can see what it indicates as being too hot, this being said, the hottest I've ever seen it is about 180 in the summer, unloaded.

ChevyTech77 · April 13, 2011

260*f is where automatic transmission fluid starts to break down, and turn to a black tar like substance. I don't like running them over 200-210*, from experiance.

dewfpo · April 13, 2011

If you have a copy of the service/repair manual for your 2011, it should say in there, what ATF temp trips the DIC warning message. That being said, if your tranny uses DEX VI then your better off sending an email to Mobil1 or whatever brand you use and they can tell you what the specifics are for their product dino or synthetic. That would give you some soild data points.

The DexIII in my '05 Allison gets as high as 210F on a 95F day when empty. Using T/H brings it down 10-15F even when empty and empty it typically runs 90-100F over ambient.

My manual says the HIGH ATF Warning comes on at 275F.

DEWFPO

OH1 · April 14, 2011

I use mine as more of a comparison. I know where it sets normally when loaded and unloaded.

If it is higher than normal i start to invenstigate.

Debo511 · April 14, 2011

Usually 20 degrees below ECT , normal driving.

20Silverado11 · April 14, 2011

Thanks for the replies and good information. From what I've heard:

- A GM Tech advises that running over 210 is not advisable

- The fluid starts to break down at 260

- The warning appears at 275 (on an Allison)

And that if you switch to the Tow/Haul mode, somehow the Allison switches into some other mode (or enables additional cooling or shift pattern) that helps reduce transmission temperature by 10-15 degrees F. Do I have the above correct?

dewfpo · April 14, 2011

In T/H mode the tranny locks the convertor in more gears than just OD. This causes less heat buildup from the torque convertor slippage. It also keeps the transmission in gears over a wider rpm range. Fuel economy is not the goal in T/H mode. Vehicle control and lowering heat in the ATF in the main concern with T/H mode.

My atf is often at 210F in the summer and it is still cherry red and shifts fine. I think 210F is a little low to worry about ATF, even dino ATF. Switching to a synthetic ATF is always a good thing since synthetics can handle the heat better.

DEWFPO

HawkScot · April 14, 2011

On my 2008 Yukon XL Denali (since traded in), if I was towing, the trans temp came up to the engine temp (around 210). It would stay at 210 until the engine temp started to rise, tracking close to the engine temp and then going a bit higher. When engine temp was ~225, trans temp was ~235. I backed off a bit towing up the mountain pass at that point and it did not rise more than that. After crossing the summit, the trans temp starting dropping when the engine temp did and followed it down to 210. The engine temp stayed at 210 (normal operating temp) and the trans cooled further, down to 190 or so. A member on the RV forum emailed GM and received an answer back quoted here...

Good Morning! Thank you for giving me the time to do some research on your concern with the transmission temperature. I have consulted one of our dealers and am happy to inform you that I have the information you’ve requested. The normal operating temperature is between 160°F to 200°F (71°C to 93°C). For towing, the normal operating temperature is between 235°F (113°C) to 260°F (127°C).