This is interesting to hear. Maybe I just need to adjust my thinking. My camper weighs about 6000lbs.
Here's a link to my research saga, in case you're interested.
https://www.tahoeyukonforum.com/thr...towing-in-the-summer-heat.125753/post-1562470
And on the transmission fluid temps, here's what GM has to say:
In the February 2011 issue of Trailer Life magazine RV Clinic in response to a reader about the maximum transmission temperature allowed in a 2009 Chevy Silverado, the Tech Team had this response.
“General Motors’ in-house towing team expert provided RV Clinic with this statement: The maximum allowable automatic transmission fluid temperature is dictated by the transmission oil itself. The oil begins to degrade significantly above 270 degrees Fahrenheit, so we design vehicles so that in all but the most extreme conditions, the fluid temperature in the transmission sump stays below 270 degrees F.
We allow for up to 285 degrees F in extreme conditions (i.e. towing a trailer with combination loaded at GCWR in Death Valley). But for customer usage anywhere else in the country, even at GCWR, transmission sump temperature should stay well below 270 degrees F. Above this point, certain internal components, such as seals, begin to disintegrate rather quickly. Although newer synthetic fluids can withstand higher temperatures we still recommend this (270F) as a maximum temperature."
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And finally, some wisdom from another member here several years ago who also towed a heavy camper with his Tahoe:
"The weak link in an automatic transmission is the fluid. All of the other components can handle the elevated temperatures. As I mentioned earlier, Dexron VI starts to degrade severely at 270°. So I was not concerned that the transmission was running at 230°. I confirmed this with a close friend, who is a transmission engineer at GM. I respect and trust his opinion.
Aftermarket coolers are discussed frequently, but the bottom line is that they're unnecessary, particularly with Dexron VI transmissions. The manufacturers test their vehicles under "worst case" conditions. You can go to Arizona, Death Valley or Pikes Peak, and you will surely see some test mules loaded up with instruments and sensors.
As an aside, I've been in the seal business for over 20 years. About a third of my business is to Tier 1 automotive suppliers, including transmission manufacturers. I call on companies like ZF, Aisin, and Master Automatic. It's my job to know how my products, and rubbers and plastics in general, are affected by elevated temperatures."
