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RyanB

GM Transmission Temps

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RyanB

My main tow vehicle is my RAM CTD, but when we take the RV as well the truck has to pull it. So then we use my 2011 Yukon XL Denali to tow the Bu. 

It has always run hot - both engine and transmission. Especially in the mountains. 

Last week we went on vacation. Pulled the boat to Steamboat, Colorado. This was up I70 to Hwy 40 for those familiar with the area. Going up it wasn’t terrible but coming home it was. Up Rabbit Ears pass, I ran it somewhat hard up until about a mile from the top. Engine temp was about 3/4 up the gauge but the transmission temp is what was worse. Even slowing down to run about 4000 RPMs in second, it was 254* at the top. 

I ran slower up to the Eisenhower tunnel, but couldn’t keep the tranny below even 240*. Again at the top, it was at 250* - even though I further slowed down. Trying to force it out of 2nd and into 3rd didn’t help (and it was hard to maintain any speed in 3rd). 

I’ve asked two GM dealers as well as an independent transmission shop about it in the past and they told me that is just what to expect towing 7000 pounds with a half ton SUV through the mountains and that it would be fine for short periods of time at those temps. 

Is anyone else seeing that high of temps?  Is there some sort of idiot light that will come on or will the engine defuel if the temps get too high?

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boardjnky4

You may want to invest in an aftermarket trans oil cooler.

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RyanB
17 minutes ago, boardjnky4 said:

You may want to invest in an aftermarket trans oil cooler.

It came with an aux transmission cooler as part of either the tow package or the Denali trim. Can you add a second one?

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oceanbu

I have a 2011 Yukon Denali and experience the same temps when towing on the Coquihalla up some of the steep elevations especially at the snow shed.  If you have ever watched Highway Thru Hell the snow shed incline is the one they call "The Crusher".

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RyanB

Just testing out a photo as a supporter. 

19FACBD5-E4CB-4B08-9340-A0B5A5B65035.jpeg

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Nitrousbird

You can put a much larger cooler on that.  I (which ended up being needlessly) put a much larger cooler on my Escalade EXT.  There is a company that sells an adapter kit that makes it a nearly bolt on swap, though I recommend replacing both tranny lines as they are prone to leaking at the joints where the flex line meets the hardline.

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Sixball

I have been out of the auto business since March 2002. Over the years I was looking at vehicle data from our testing GM always had hi trans temp. Much higher then ours. Under load or not. Cant say they had more failures or not. never did much endurance work.  I would also go with more cooler. I have not pulled a big load with the new 10 speeds. They are a joint  engineering with Ford /GM both with each own calibrations. I don't want to load a trailer for a teat run if I don't need to pull somewhere.

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Falko

Short period of time or not, 250+ is a bit hard on the transmission. Spend $500 now on a better cooler or $4000 later on a new transmission.

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BlindSquirrel

Most trans cooler systems have a valve that opens to the cooler when needed and closes when not. Both my and your ctd has one, not sure on the Yukon. Could be gummed up and stuck in the closed loop.... if it has one.  

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Nitrousbird

Here are the parts I used for my upgrade and what I paid at the time, though that was a couple years ago:  

- Tru-Cool Max 40,000 GVW Transmission Cooler, P/N OC-4739-1 ($118.50, eBay, usa.industries seller)
- Adapter Kit to make cooler fit factory lines/location (Modern Muscle Salvage, $75)
- Short Cooler Line - AC Delco 15779543 (Amazon $14.89)
- Long Cooler Line - AC Delco 25999420  (Amazon) $64.22

The lines aren't necessary to replace, but are known to fail, so I would.

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RyanB
2 hours ago, Nitrousbird said:

Here are the parts I used for my upgrade and what I paid at the time, though that was a couple years ago:  

- Tru-Cool Max 40,000 GVW Transmission Cooler, P/N OC-4739-1 ($118.50, eBay, usa.industries seller)
- Adapter Kit to make cooler fit factory lines/location (Modern Muscle Salvage, $75)
- Short Cooler Line - AC Delco 15779543 (Amazon $14.89)
- Long Cooler Line - AC Delco 25999420  (Amazon) $64.22

The lines aren't necessary to replace, but are known to fail, so I would.

That is the one I have been looking at and will be installing. 

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Nitrousbird
1 hour ago, RyanB said:

That is the one I have been looking at and will be installing. 

It is fairly easy to install.  You have to cut one the short line to turn it 180 degrees but it is pretty easy to do.  Good time to do a full transmission fluid replacement as well.  I recommend the following:

Keep one of the old transmission lines you should be replacing and cut the end off several inches after the radiator connector.  Put a long rubber tube from that to a container and attach it to the output of the radiator.

From there, have someone start the truck and run it until you first start seeing bubbles in the rubber line.  Shut off the truck, add fluid and do it again until you get all of the old stuff cycled out.

This is the safe way to do it.  No flushing, which can cause damage.  Dropping the pan doesn't change out much fluid.

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RyanB
31 minutes ago, Nitrousbird said:

It is fairly easy to install.  You have to cut one the short line to turn it 180 degrees but it is pretty easy to do.  Good time to do a full transmission fluid replacement as well.  I recommend the following:

Keep one of the old transmission lines you should be replacing and cut the end off several inches after the radiator connector.  Put a long rubber tube from that to a container and attach it to the output of the radiator.

From there, have someone start the truck and run it until you first start seeing bubbles in the rubber line.  Shut off the truck, add fluid and do it again until you get all of the old stuff cycled out.

This is the safe way to do it.  No flushing, which can cause damage.  Dropping the pan doesn't change out much fluid.

From this review, it sounds like the current kit may have addressed your first sentence.

Either way, this likely isn't something that I will tackle myself.  I know you do a lot of this, but it isn't something I enjoy doing, and with as much as I travel for work, I'd rather spend that time doing something other than this project.

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carguy79ta
8 hours ago, Nitrousbird said:

It is fairly easy to install.  You have to cut one the short line to turn it 180 degrees but it is pretty easy to do.  Good time to do a full transmission fluid replacement as well.  I recommend the following:

Keep one of the old transmission lines you should be replacing and cut the end off several inches after the radiator connector.  Put a long rubber tube from that to a container and attach it to the output of the radiator.

From there, have someone start the truck and run it until you first start seeing bubbles in the rubber line.  Shut off the truck, add fluid and do it again until you get all of the old stuff cycled out.

This is the safe way to do it.  No flushing, which can cause damage.  Dropping the pan doesn't change out much fluid.

I changed the fluid in my 13 2500 CTD like that. It was a pita due to the thermal bypass valve, but got it done. The tranny took about 3.5 gal by the time you pump out the old stuff while the pump is sucking in new stuff. Did it at 75k. Old stuff looked pretty good. Surprised since it is an      rfe 68 with200hp tune. I think I will be good for 100k before nx change

 

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RyanB

TruCool is getting installed today.  I won't use the Yukon to tow the Bu until the end of the month.  Interested to see how it does.

I've searched high and low, and I can't find anything that says what the operating temperature range is of the Dexron VI fluid.  I did speak with one transmission shop that said they are fine up to 260 - 270*, but man that seems hot to me.

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RyanB

@Nitrousbird, when you installed the TruCool in your Escalade, did your outside temperature continue to work?  Reason I ask is that my outside temp never worked when towing - always read at least 10* high.  Now with the new cooler installed, it is even less accurate.  After a rain storm today, temp dropped to about 80*,  yet when I drove the Yukon, it was showing 99* and rising.

From looking, the temp gauge is installed behind the grill, in front of the radiator.  It looks like it may be blocked by the new cooler.  The part is cheap to change out if it has just gone bad, but with it directly behind the cooler now, it wouldn't surprise me if it can't work properly in that location.

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Nitrousbird
16 hours ago, RyanB said:

@Nitrousbird, when you installed the TruCool in your Escalade, did your outside temperature continue to work?  Reason I ask is that my outside temp never worked when towing - always read at least 10* high.  Now with the new cooler installed, it is even less accurate.  After a rain storm today, temp dropped to about 80*,  yet when I drove the Yukon, it was showing 99* and rising.

From looking, the temp gauge is installed behind the grill, in front of the radiator.  It looks like it may be blocked by the new cooler.  The part is cheap to change out if it has just gone bad, but with it directly behind the cooler now, it wouldn't surprise me if it can't work properly in that location.

Never had an issue before or after the cooler install, it was always pretty accurate (at least after a mile of driving).

If your front grill is easy to remove, I would start with swapping the sensor.  If it is a royal PITA like my Escalade (where you had to remove the front bumper), I would replace AND relocate all at once. 

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hunter77ah
16 hours ago, RyanB said:

@Nitrousbird, when you installed the TruCool in your Escalade, did your outside temperature continue to work?  Reason I ask is that my outside temp never worked when towing - always read at least 10* high.  Now with the new cooler installed, it is even less accurate.  After a rain storm today, temp dropped to about 80*,  yet when I drove the Yukon, it was showing 99* and rising.

From looking, the temp gauge is installed behind the grill, in front of the radiator.  It looks like it may be blocked by the new cooler.  The part is cheap to change out if it has just gone bad, but with it directly behind the cooler now, it wouldn't surprise me if it can't work properly in that location.

Mine still works after I installed mine. I relocated it when I had to pull off the front bumper.

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RyanB
47 minutes ago, Nitrousbird said:

Never had an issue before or after the cooler install, it was always pretty accurate (at least after a mile of driving).

If your front grill is easy to remove, I would start with swapping the sensor.  If it is a royal PITA like my Escalade (where you had to remove the front bumper), I would replace AND relocate all at once. 

 

43 minutes ago, hunter77ah said:

Mine still works after I installed mine. I relocated it when I had to pull off the front bumper.

Thanks for the feedback. Youtube makes it look like I don’t have to take off the front bumper (I saw that you need to on the Tahoe). I think I’ll still replace and try to relocate at the same time. 

Why is there always another project???

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hunter77ah
15 hours ago, RyanB said:

Why is there always another project???

I ask myself the same question! Good luck with the install!

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RyanB

Paying more attention to temps now. After the install of the new aux unit on the Yukon i drove 40 miles on the interstate on Monday morning. It was cooler ambient probably 70. Yukon trans temp gauge showed a high of 127. 

Rented a new Traverse in Nebraska. On the way from Lincoln to Omaha I saw this type of temp. 90* ambient. 

Chevys must just run hot. 

104E69A8-CAF8-4F42-A601-C344B3078E22.jpeg

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RyanB

Towed the boat for the first time since I had the new trans cooler installed. 

Just flat land down I76 and back. Cruise set about 70 MPH, outside temps in the low 90’s,  most of the time in 5th gear running about 2400 RPMs, the trans never got above 180*. It spent most of the time in the 160* range. Before the cooler install it ran 200* - 220* on this same trip. Must say so far I am pretty impressed. 

I’ll give it more of a test next week as we will be using it to tow the boat to Utah. The ride home will be the real test - eastbound over Vail Pass and the Eisenhower tunnel is where it would run up to 250*+ before. Will report back again. 

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jjackkrash

Yup, the Ike Gauntlet is a pretty good test.  :)

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