I am curious what those of you that are towing with your full size GM SUVs are seeing for transmission temps when towing?I use my 2011 Yukon XL Denali as a secondary tow vehicle for my 7000ish pound boat. Two weeks ago I was coming back from the lake towing eastbound on I70 in Colorado, and saw temps between 220 - 250 going over Vail Pass and Eisenhower.Last year I noticed temps above 220, and two dealers told me that was within normal expectations with that load going up the passes, but it seems high to me.My Yukon has the aux transmission cooler as original equipment, about 85,000 miles on it, and I did a drain and fill on the transmission fluid probably 10,000 miles ago.Photo of my set up. It does tow level, the photo is at a bad angle.

That's pretty close to what I saw with my 5.3l Tahoe. Pretty normal unless its an Allison, those run a lot cooler. I put about 40,000 towing miles on my Tahoe and transmission is still healthy at 185k miles with just normal fluid changes. I do have Dexron 6 in it because it holds up a bit longer to heat than Dexron 4, but you need to do a full flush if you switch over.

250 is pushing it a little, for a short period with high ambient temps while towing is one thing. If you start seeing that consistently then that's completely different. Where are you getting the readings, the factory stepper motor driven gauge or digital readout?I'd say normal although I've never seen more than 205 on multiple GM trucks both 1500 and 2500. That was pulling a 5 mile long grade in excess of 15% in places here in PA with ambient above 85.

Ralph Cramden wrote:That was pulling a 5 mile long grade in excess of 15% in places here in PA with ambient above 85.Wow, that would take you 700 feet above the highest mountain in PA, and that would be if you started at sea level.

250 is too hot, you don't want to be over 225. I would look into a larger aux cooler. My Suburban came from the factory with 2 coolers. Fluid passes first through part of the radiator and then through an external cooler. Even on the hottest day going up a steep hill I have never seen more than 205, and our TT is 8500 lbs.

Use a synthetic Dexron 6 fluid. Change fluid regularly, I change every 50,000 miles. Check fluid regularly, if brown or smells burned then change. I also installed a Derale auxilliary cooler, with built in fan, off to the side of the OEM cooler. Cooler is better! However, 250 is ok if it is a spike and immediately pulls back down. If transmission is hot always let it idle to cool down, never turn it off if hot. If you are pulling upgrade and it gets hot, pull over let it idle fast so that the fan will pull the temperature down and then resume on up the hill.

GM Full Size SUV Transmissions Temps? | Good Sam Community

16 Replies

APT
Explorer
May 18, 2018
250 is higher than I'd like to see. I think if I saw 230 on a regular basis, I'd get a larger capacity transmission cooler. Under $75 in parts and maybe $250 for any transmission shop to install.
rwess
Explorer
May 18, 2018
Use a synthetic Dexron 6 fluid. Change fluid regularly, I change every 50,000 miles. Check fluid regularly, if brown or smells burned then change. I also installed a Derale auxilliary cooler, with built in fan, off to the side of the OEM cooler. Cooler is better!
However, 250 is ok if it is a spike and immediately pulls back down. If transmission is hot always let it idle to cool down, never turn it off if hot. If you are pulling upgrade and it gets hot, pull over let it idle fast so that the fan will pull the temperature down and then resume on up the hill.
BurbMan
Explorer III
May 18, 2018
250 is too hot, you don't want to be over 225. I would look into a larger aux cooler. My Suburban came from the factory with 2 coolers. Fluid passes first through part of the radiator and then through an external cooler. Even on the hottest day going up a steep hill I have never seen more than 205, and our TT is 8500 lbs.
Lynnmor
Explorer II
May 18, 2018
Ralph Cramden wrote:
That was pulling a 5 mile long grade in excess of 15% in places here in PA with ambient above 85.

Wow, that would take you 700 feet above the highest mountain in PA, and that would be if you started at sea level.
Ralph_Cramden
Explorer II
May 18, 2018
250 is pushing it a little, for a short period with high ambient temps while towing is one thing. If you start seeing that consistently then that's completely different. Where are you getting the readings, the factory stepper motor driven gauge or digital readout?

I'd say normal although I've never seen more than 205 on multiple GM trucks both 1500 and 2500. That was pulling a 5 mile long grade in excess of 15% in places here in PA with ambient above 85.
bartlettj
Explorer
May 18, 2018
That's pretty close to what I saw with my 5.3l Tahoe. Pretty normal unless its an Allison, those run a lot cooler. I put about 40,000 towing miles on my Tahoe and transmission is still healthy at 185k miles with just normal fluid changes. I do have Dexron 6 in it because it holds up a bit longer to heat than Dexron 4, but you need to do a full flush if you switch over.

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GM Full Size SUV Transmissions Temps?

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