Engine And Transmission Get Hot When Towing

2002bowtie · June 17, 2011

I live here in AZ and drive through the salt river canyon a few times a year towing my trailer witch is only about 3000 lbs. I case you don't know the salt river canyon is a very long and very steep mountainous curved road. When it is over like 90 degrees outside my transmission easily gets up to 230 degrees then I make sure to let off to cool down. When I say let off I mean like 15-20 mph. Also on the really steep straight grades my engine will easily get up to 230 or so. And that is not really accelerating that much just trying to make it up the hill. Has anyone else had this problem or know of any solutions I have a 2009 GMC Sierra 2wd crew cab with the 5.3 and a 6 speed an 3.42 rear end and 285/70/17. I am contemplating a blackbear tune, transmission and/or engine oil cooler, also maybe 4.10 rear end. Any advise please help.

I have also noticed the same thing driving my mother inlaws 09 GMC yukon with 5.3, 6 speed and 3.42 rear end but stock tires and it does the same thing.

HawkScot · June 17, 2011

I can't speak for your truck, but was told my 2008 Yukon XL Denali 6.2/6sp/3.42 could run that warm and it was normal. Another RV person emailed GM and got this response.

I was also concerned at one pointhowever and contacted GM with the question. There answer was: 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).

oldschool327 · June 19, 2011

Dp you have the facotry tow package with the tranny cooler?

Suggest you run a trans cooler for better protection. B&M make good ones that fit nicely.

I run the factory cooler, a Mag HyTec deep pan, and never see over 180. At 230 your trans fluid will degrade faster than normal.

2002bowtie · June 20, 2011

Both vehicles have tow package and factory transmission coolers. And I don't know of any company that makes an aftermarket pan for the 6l80.

txab · June 20, 2011

Both vehicles have tow package and factory transmission coolers. And I don't know of any company that makes an aftermarket pan for the 6l80.

You can always add a larger cooler.

stingerz16 · June 21, 2011

I can't speak for your truck, but was told my 2008 Yukon XL Denali 6.2/6sp/3.42 could run that warm and it was normal. Another RV person emailed GM and got this response.

I was also concerned at one pointhowever and contacted GM with the question. There answer was: 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).

are these temps in reference to the transmission? i am seeing around 210 when towing...freeway cool day.

I have not towed up steep grades on a warm day.

when should i be worried? around 250+ for trans temps?

i have the towing pkg with trans cooler.

mdauwald · June 22, 2011

Years ago I used to drive that canyon about a dozen times a year and whether I was towing or not my vehicles always ran warm going up the other side. I approach 210 towing up the slight grades around here. I believe the solution is to have more frequent transmision service intervals for tow vehicles. I have always serviced my automatic transmissions every 30k. Some last and some don't. My last GM transmission (700R4) only lasted 120k before a pump failure and the 4.3 threw a rod 2K miles later so rigid maintenance doesn't always save you.

Knowklew · June 22, 2011

I recommend a 6.2 NHT truck....but then again I'm a little bias

2002bowtie · June 22, 2011

To be honest I wish I got the 6.2. But this will have to do for now. My 230 temps are for the transmission and engine, they both get hot.

Stevens03 · June 22, 2011

Unless your approaching the red on the gauge, GM's not going to see it as a problem. I've yet to see my gauge move above 210 but I've not had anything heavy to tow yet either

Knowklew · June 22, 2011

The dummy gauge on the dash is usually not very accurate nor does it really show any real change. I recommend getting a dashhawk or Aeroforce Interceptor type gauge to truly monitor what the real temps are.

When I had my TBSS I was deathly afraid when my trans temps got over 220. I installed a large aftermarket trans cooler to help. Heat is the mortal enemy of a transmission.

I say regear, 3.73 or 4.10.

07VMax · June 23, 2011

i pulled 4-5k up am 8% grade for 6 miles i think at 90 degrees outside and my truck ran about 220 engine temp and 217 trans temp, i was pulling the trailer for two hours before this hill clime this is on an 07 vortec max ext cab 4x4 3.73 and 285/70/17 MTR's.

wavery · June 23, 2011

I live here in AZ and drive through the salt river canyon a few times a year towing my trailer witch is only about 3000 lbs. I case you don't know the salt river canyon is a very long and very steep mountainous curved road. When it is over like 90 degrees outside my transmission easily gets up to 230 degrees then I make sure to let off to cool down. When I say let off I mean like 15-20 mph. Also on the really steep straight grades my engine will easily get up to 230 or so. And that is not really accelerating that much just trying to make it up the hill. Has anyone else had this problem or know of any solutions I have a 2009 GMC Sierra 2wd crew cab with the 5.3 and a 6 speed an 3.42 rear end and 285/70/17. I am contemplating a blackbear tune, transmission and/or engine oil cooler, also maybe 4.10 rear end. Any advise please help.

I have also noticed the same thing driving my mother inlaws 09 GMC yukon with 5.3, 6 speed and 3.42 rear end but stock tires and it does the same thing.

I'd suggest a pusher fan for your trans cooler. I wired mine in with a relay. The fan is powered from the battery (with an inline fuse) and the relay is activated by a wire that I spliced into the radiator fans. That way, when the radiator fans come on, the trans fan comes on also. It makes a big difference both in trans temp and engine temp. I would also suggest synthetic trans fluid (for those that don't already use it).

Petrol based ATF is an insulator and does not like to release heat. Synthetic oil releases heat at nearly the rate of water. The other advantage is that petrol based ATF will literally "burn"...... it's an organic material. Synthetic will not burn and won't break down until ~600* (long after the seals fail).

If you switch to synthetic, be sure to get all of the ATF out of the converter. There is an easy way to accomplish this. Most of the 4L60E trans hold about 9 qts (4 in the oil pan and 5 in the converter). Start out by buying 10-12 qts of synth ATF, a new filter and trans pan gskt. Pull the pan (clean it), replace the filter. Replace the pan and fill the pan until the dipstick says full (do not start engine). Remove the return cooler line from the radiator. Put a rubber hose on the line and run the hose into a clear container that has "1 qt" measured and marked on it. Start the engine and let it idle until 1 qt of ATF flows into the container (around 10 seconds). Shut-off the engine and add one qt of synthetic ATF to the trans. Dump the fluid from the clear container. Repeat this process until you see a change in the color of the fluid pouring into the container. This should take the remainder of your 10-qts. If you have an over-sized oil pan it may take more. You are better off buying more ATF than you need, you can always return what you don't use.

If your vehicle is just a daily driver, you should not have to worry about changing the ATF for another 100K miles. If you tow moderately, 60K miles. If you tow heavily, 40K miles. The bottom line is, synthetic will never burn but it can get contaminated by moving parts wear. The heavier that you tow (race or mountain drive), the more wear that you will experience.

Hope this helps.

This is my trans cooler set-up:

This is my engine and trans temps towing 4,000# in 90* temps. My guage is a "ScanGauge" it works off of the ECM reported values. Extremely accurate.

jerksville · June 23, 2011

Been thru there hauling a 1970 Chevelle I picked up from Queens Valley. That canyon is brutal and my truck got hot as hell there two. Id say that it would be a good idea to add an aux. tranny cooler. Keep in mind when you have the AC on there is hot air coming from the condensor and passing thru the radiator which slow the cooling ability if the radiator.