Last week i was going to Duck Creek Village, Utah. The last twenty or so miles of the drives is fairly steep up hill, during the time i noticed that my trans temp was heating up slowly going up the hill. The truck was in tow haul mode and i was towing an enclosed traier with a rhino, several quads and a dirt bike.
My temp had to of been in the 280 to 290.. The DIC had a flash come up saying the transmission temp was Hot. I quickly pulled over at the next turn out. And let the truck cool down. My question is does anyone think this causes serious damage? You could smell burnt fluid. I was thinking just flush the fluids and put new filters on. And i have a mag-hytec trans pan.

The truck only has a turbo back exhaust no tune

Computer gave you a warning, you stopped as soon as possible and let it cool down, I'd say no worries. I agree to check/change fluids/filter on Tranny. I don't know how much of one is built in, but I am sure that GM has a "factor of safety" built into the "red zone" temps for engine/tranny and for the temp that the DIC gives you a warning message. I bet these are set below the actual "danger" temps.

ok thanks. I figured that I couldn't of done too much damage. The stranger thing is my dad was behind me towing the fifth wheel, which is 39 feet and weighs over 16,000. He tows it with a 2008 Lmm dually. And our other friend has a 2007 classic CCSB like mine he was toying a weekend warrior thats about 35ish feet i believe and none of them had their temps going much over 240 to 250.

What would of caused mine to??

Been there. Get a Mile L cooler and run the deep [an with Transynd or Mobil Delvac ATF. Both Chevy and Allison recommended this to me.

I was curious if you were in 1st gear on the way up the hill? It's the only gear in T/H that doesn't lock up. You'd be going VERY slowly if this were true. The best way to climb steep hills is get it into second gear, then hold it with manual, making sure not to over-rev the Dmax. 2nd gear gets you into TC lockup, and also gives you good torque multiplication. If you did all this and it still got hot, then I'd say your reaction plan was the best any of us could do.

If you suspect that's going to be a repeated routine, I'd strongly suggest an upsized capacity tranny cooler. We have good vendors here to can assist you.

Question for dnewton: My near overheating DID result from slow speed during a heavy, steep pull in very hot weather (transmission went into what I call mush-mode but threw no codes). I was in TH. Temp hit about 260 on the gauge — just bumping the red zone. I could not have gone fast enough to get TC lock-up (which I understand is 25-30 mph). Road was full of hairpin turns and steep. Could I have started out with enough speed to get into 2nd and then gone to manual as a way to keep the converter locked (presuming that would pull the grade). Or will I get a downshift to 1st? My situation was the necessity of being off and on the throttle and never off over about 25 mph.

We were going maybe 20 mph thru some of the hills and sometimes 30. I don't remember what gear it was in. But the last big hill i was maybe doing in the mid to high twenties. Once i saw the temp gauge as high as it was and the warning come up. I was more focused on finding a spot to pull out and let it all cool back down. My dad asked me to what gear I was in. The odder part is the year before I towed a 31 foot next level toy hauler and never saw an issue. And that had plenty more toys in the back of it

Would swapping out the transmission cooler allow any of the dealers to hassle me??
Our friend works as a service writer in huntington and he seems to allow most things, i was just wondering if i have to go to another dealership

I would say the MikeL. cooler the dealer wouldn't have any issues with. I'm running a different cooler but it's not a bolt on like Mike's. Go with Mikes if your worried about dealership issues for warranty work. I belive he said a 20-30 degrees drop in temp.

Desert — your situation was exactly like mine. The TC does not lock up at those speeds. Dealer and Allison (both knew of this problem with others) said "larger cooler, Transynd, deep pan." Later, the dealer wanted to look at the new cooler I had installed and wanted to know how it works. So far it is fine, but I have not yet duplicated the original problem situation (but may do so soon). It does run cooler, however. Cooler swap is easy. So is deep pan and Transynd from Allison.

Thanks guys, ya well tomorrow i am going to have the fluids and filters flushed and replaced with synthetic by oc diesel, they put my pan on a few years ago. This sunday i will be going to the same camp ground and doing the same grade, even towing the same atvs, rhino and dirt bikes. Any one else got any recommendations??
Like no a/c.... if that really helps. Weather is in the 60's

Or should I try it again the same way it was before and maybe lock it in third gear or another gear and see if the problem is still there.

I would be so upset if there was any damage done to my transmission... haha that just means it gets to be beefed up sooner :D

One more item is worth mentioning. On the 2007 Classic like mine (don't know about the 2006 models), there is not a proper license plate mounting bracket available. It took me a while to discover this. The dealer, in mounting my plates, mounted them so that they would lie flat — which requires mounting them through the bottom holes. But this extends the plate upward and over the air intake for the transmission cooler. I've since built some nice spacers and mounted the plate downward through the top holes — uncovering the trans cooler air intake. Check to make sure that your trans cooler air intake is not obstructed. BTW, I don't believe that you can lock the transmission in a given gear. In fact, I don't believe that you can use the manual and lock it in 2nd. IIRC, I was told by Mike L that that the converter locks up and drops out in relation to speed. It's not something you can define.