Can anyone tell me what kind of transmission temp I should expect to see while towing TT? TV is GMC1500 with Tow Pkg. TT is 7000lb. I've been seeing about 185 deg driving on mostly flat terrain @ 60mpg.Outside temps 80 -90. Normal trans temp is around 160 deg. I'm new to towing and just have no idea how hot is too hot. Thanks

Thanks for that. At what temp should I be concerned?

The OEM trans cooler in out TV (see sig) was about the size of an average hard-cover book and tucked safely behind the GMC logo. I replaced it with one that was about a square foot and installed it to one side where the air could actually hit it. It was only about $110 in Canada so it would be like $59.95 in the States and was quite simple to install.Dropped trans temps about 10 deg C across the board.Stu

Thanks Stu. I have heard that OEM coolers really weren't that efficient. I will look into a replacement. But as I said I have no experience so don't know what temps should be running.

Fears about inadequate cooling are somewhat unfounded. So long as you are towing within rated capacities, GM says that cooling is sufficient and I personally have found that to be true. I towed 2 different travel trailers with my old '03 Trailblazer, one of them through mountains without an axillary cooler. I had 160k on that truck when I sold it, the trans was as strong as ever. I towed though mountains with a '95 'Burb and that truck has 190k on it now, no axillary cooler, and my dad is still towing a TT with it. Trans is as strong as ever. Both of these have the 4L60E as does my current Sierra. What year is your GMC? In 2006 they switched trans fluid to Dex VI which is full synthetic and does wonders to help in cooling. If you have a TV that older than 2006 I suggest you switch to Dex VI if you haven't already. You can run the trans up to 220 without damage, but watch the amount of time you do so. Even a bit over 220 for very short periods won't hurt it.

Transmission temps | Good Sam Community

steiny93
Explorer
May 13, 2014
I have a tracked jeep that I've been fighting tranny temp issues with. Working through that I've dug into the problem quite a bit; in my scenario I couldn't get enough air flow due to the slow ground speed and had to add an aux cooler to cover the differential between my need and the factory setup.

Anyway,
Hot tranny's = dead tranny's; you want to keep the temp within manufacturer operating temps as much as possible. If your torque converter is not locked up you will generate a ton of heat; even with the tow/haul option dropping out of overdrive can help reduce temps (some tranny's do not lock up in OD). Staying around 200 degrees is a happy place, bumping up against the manufacturer limp mode limit is going to take a lot of life out of the tranny.

Aux coolers make a significant difference; the trick is to get a large enough btu rating to cover the need. On my jeep I was able to go from 270+ and climbing to staying under 200 regardless of the load.
rwess
Explorer
May 11, 2014
The Dexron VI OEM fluid that comes in GM vehicles is not a full synthetic fluid, it is a blend. For some reason most people believe that when GM changed to the Dexron VI it was to upgrade to a full synthetic. If you check on the internet, or go to Bob's the oil guy website you will find a list of non OEM Dexron VI manufacturers. There are only a few that actually make a full Dexron VI synthetic that are approved by GM. When I changed the fluid in my 2010 2500HD with the 6L90E transmission I used Valvoline. It is a true synthetic. I also always add a bottle of LubeGuard. I once had a transmission guy tell me that he always used a bottle of Lubeguard in every transmission that he repaired.
ib516
Explorer II
May 10, 2014
I wouldn't "worry" unless you hit over 230*. Of course the higher you go, the less time I'd want to be there. My 2007 RAM 3500 would lock out overdrive on it's own and light the "TRANS TEMP" idiot light at 260*F - not that I ever had it happen, but that's the temp the OEM deemed unsafe. Not sure where that level is on the new 2014.
Iraqvet05
Explorer
May 10, 2014
My Silverado 1500 also runs about 80-100 degrees above ambient temp. On a trip last year with high humidity and the outside temp around 100, the trans temp was running 200-210 pulling 5500 lbs in some hills. I was tempted to replace the small factory cooler with a Tru Cool cooler.
Bull_Rider
Explorer
May 10, 2014
Mine runs at about ambient air temp plus 80-100 degrees. So today, towing north from Rupert Idaho to Pendelton Oregon it was running at about 150-175 degrees.

That's pulling a 8k bumper pull at 65 MPH.
mosseater
Explorer II
May 10, 2014
The other component to this is where the sensor is located. I'm no expert, but I've read accounts that because of sensor placement within the fluid system, the actual fluid high temp could be higher, or at least make the reading lag behind what the actual fluid temp is. Sensor in pan or right after cooler will read differently in the same truck at the same temps. It makes sense that this might be true, but I admit I don't know for sure. I have an infrared thermometer that I shoot the pan with and it reads around 185-200 most times while towing in the summer. I have seen it spike to 230 on occation after a long steep hill. I also change my fluid at 30K intervals.
Fast0ne
Explorer
May 10, 2014
Well I don't have your truck I have a chevy colorado with the 4 speed auto.

On this truck the computer will put the tranny into safe mode at 270*F.

On my own truck I installed a big B&M tranny cooler and it droped the temps by 20* degrees. Now when towing in the summer heat and going up some big hills here in bc canada with a/c on I am not even breaking 170*F and that's towing 3rd gear. On the flats I run about 150*F.

So a cheap but good investment add a tranny cooler.
jfkmk
Explorer
May 09, 2014
goducks10 wrote:
Are you using the tow haul mode?

If you don't have a tow mode, tow in 3rd. I added an auxiliary tranny cooler to my tow vehicle. It was about $50 and took less than an hour to install.
Campfire_Time
Explorer
May 09, 2014
lasttruck wrote:
Some where on the web is a nice chart that shows transmission fluid life based on temperature. The higher the fluid temps, the shorter the it's life.

I found it!

http://www.txchange.com/heatchrt.htm
mleekamp
Explorer
May 09, 2014
I will also note, YES we use Tow/haul mode, and its important to note that if we slowed down about 5mph from what we were at, temps dropped. Yes, I am guilty of trying to drive 65 or so towing at times....but if I slowed to 60 for awhile it was fine.

Like i said before, we checked the fluid once per year to ensure its not "burnt" or in need of replacement