Replace Transmission Cooler with TruCool 40k

[Cory Dorning]

I have an 08 XL Denali with a stock cooler and am looking to replace it with a 40k but have a few questions...

- which 40k cooler do I need (thermal bypass or not)? I live in Northern Kentucky and tow a 7k lb travel trailer

- what other equipment/parts/tools would would I need to install this?

- considering doing it myself but depends on the difficulty. Any good videos of this out there? I searched but couldn’t find a Yukon specifically.

Thanks for any help you can provide.

 

[randeez]

https://www.performancetrucks.net/f...-fittings-hardware-508374/page29/#post5439440

Get that.

thermal bypass is up to you, i didnt install one but am also in south florida - i dont worry about it taking forever to get up to temp- it is also still going through the radiator cooler.
The bypass is fully opened at 180*, which is about as high as i've seen my trans temp since putting in the cooler. usually runs 135-140ish normal driving, if i drive spirited it'll start creeping up but i really have to beat on it for a while to see anything over 175*.
transmission does seem smoother when fluid is 120*+, so if you're seeing a lot of cold temps i would say throw in the bypass

 

[Cory Dorning]

My bigger concern is hotter temps. In upper 80* weather, I was hitting 200+ trans temp while towing. Trying to avoid that again.

Will likely go without the bypass and grab the kit you linked. Thanks!

Any install videos/guides out there?

 

[swathdiver]

I have an 08 XL Denali... and tow a 7k lb travel trailer

That's right up to the limits depending on how much the driver weighs and the how much weight the WDH can move off the tongue.

 

[Cory Dorning]

That's right up to the limits depending on how much the driver weighs and the how much weight the WDH can move off the tongue.

Yes.

 

[intheburbs]

Completely unnecessary, IMHO. Normal operating temperatures are 190-200°.

I've done this on multiple occasions, original transmission still shifts perfectly with 180k on it. 20k miles of heavy towing, including the Rockies and the Eisenhower Tunnel.

I f I were you, I'd be a lot more concerned about the rear axle than the transmission. Have you checked its temperature while towing? Have you checked your weights while towing? I'd be willing to bet it's either a) getting really hot, or b) overloaded, or both.

I'd upgrade the rear diff cover to one with cooling fins. I towed lots of heavy stuff with my half-ton Suburban, and it still has the original transmission at 250k miles, but it's on rear end number 4.

 

[Cory Dorning]

Completely unnecessary, IMHO. Normal operating temperatures are 190-200°.

I've done this on multiple occasions, original transmission still shifts perfectly with 180k on it. 20k miles of heavy towing, including the Rockies and the Eisenhower Tunnel.

I f I were you, I'd be a lot more concerned about the rear axle than the transmission. Have you checked its temperature while towing? Have you checked your weights while towing? I'd be willing to bet it's either a) getting really hot, or b) overloaded, or both.

I'd upgrade the rear diff cover to one with cooling fins. I towed lots of heavy stuff with my half-ton Suburban, and it still has the original transmission at 250k miles, but it's on rear end number 4.

Thanks for the input. I just replaced the rear shocks and suspension compressor. Had a full WDH alignment also.

Just curious but why do you suggest it's overloaded?

Just for comparisons sake, I took a 4 hour trip in 70* weather and the transmission never went past 185. Recently took a two hour trip in 89* weather and it hit 235*.

After some googling and browsing forums, just made me nervous I was running too hot.

 

[kbuskill]

It's never a bad idea, IMO, to upgrade the cooling capacity of ANY of the cooling systems in your vehicle since heat is ultimately what breaks down the fluids that are there to protect whatever system it is in.... especially the transmission.

 

[intheburbs]

It's never a bad idea, IMO, to upgrade the cooling capacity of ANY of the cooling systems in your vehicle since heat is ultimately what breaks down the fluids that are there to protect whatever system it is in.... especially the transmission.

Except, of course, if the "upgrade" prevents the system from getting to normal operating temperatures.

Thanks for the input. I just replaced the rear shocks and suspension compressor. Had a full WDH alignment also.

Just curious but why do you suggest it's overloaded?

Just for comparisons sake, I took a 4 hour trip in 70* weather and the transmission never went past 185. Recently took a two hour trip in 89* weather and it hit 235*.

After some googling and browsing forums, just made me nervous I was running too hot.

You have a 4200-lb rear axle weight rating, and a payload rating of 1500 lbs. A properly loaded/balanced trailer will have about 13% of its weight on the tongue. 13% of 7000 lbs is 910 lbs. Add the weight of your hitch, and that leaves you a little over 500 lbs for you, your passengers and all your gear. I hope you have small/skinny passengers.

Additionally, an SUV puts more if its curb weight on the rear axle, compared to a pickup. That's an additional handicap that limits how much you can carry/tow. So I ask again - have you weighed your rig to see where your numbers are? If not, I strongly suggest you do. 7,000 lbs is a lot of trailer for a half-ton SUV.

 

[kbuskill]

Except, of course, if the "upgrade" prevents the system from getting to normal operating temperatures.

This is very true... case in point, engine oil needs to get up to a certain temperature in order to burn off the condensation that occurs after cooling over night. This is one reason why allowing your engine to warm up to operating temperature is very important and why quick short trips are harder on an engine than long trips with continuous driving.

I live in Florida so not getting up to operating temperature is pretty much unheard of... lol

The transmission fluid still passes through the radiator before it goes through the external cooler which warms and helps regulate the fluids temperature and, if you do live in a cold climate, they have bypasses that are temperature activated, as I'm sure you know, which wouldn't allow the fluid to be cooled by the external cooler until up to operating temperature.

 

[Cory Dorning]

You have a 4200-lb rear axle weight rating, and a payload rating of 1500 lbs. A properly loaded/balanced trailer will have about 13% of its weight on the tongue. 13% of 7000 lbs is 910 lbs. Add the weight of your hitch, and that leaves you a little over 500 lbs for you, your passengers and all your gear. I hope you have small/skinny passengers.

Additionally, an SUV puts more if its curb weight on the rear axle, compared to a pickup. That's an additional handicap that limits how much you can carry/tow. So I ask again - have you weighed your rig to see where your numbers are? If not, I strongly suggest you do. 7,000 lbs is a lot of trailer for a half-ton SUV.

I do have small passengers actually, lol. But your point is made. I haven't had it weighed but will have it done. Thanks.

 

[mountie]

On my old truck ( '88 C2500) , I installed a transmission cooler & by-passed the radiator.
IMO, the Setrab cooler is the best out there. Pricey, but well worth it.
It's considered an engine oil cooler, but works perfect for tranny's too.

 

[drseth]

I do have small passengers actually, lol. But your point is made. I haven't had it weighed but will have it done. Thanks.

One thing I noticed once I traded my 2003 Suburban 2500 4wd with 8.1, besides gas mileage, was how much taller the diff was in my 2009 Yukon, 4.11 vs 3.42. I am getting 18 mpg calculated vs 11 mpg with the 8.1. Not sure what your Denali has, but if you take it easy, stay away from mountainous areas, you would be ok as is.

On a October cross country trip, I drove up Pikes Peak, and the tranny hit 210 once I got to the top, 14,114 feet ASL. I wish I had an external cooler, and there was just 2 of us and luggage.

In Northern KY, I would opt for the bypass. I wiuld also recommend changing the ATF with Synthetic if available every 30K, if towing a lot.

 

[swathdiver]

I wiuld also recommend changing the ATF with Synthetic if available every 30K, if towing a lot.

FYI: NNBS come with Dexron VI which is synthetic.

 

[scotts_4x]

If you look at (or call and ask) the website of any performance transmission company you will almost definitely see the proclamation that you CAN NOT over cool transmission fluid. Now I know gm employs engineers that know it all yada yada. I'll take it from guys doing a whole lot more with a trans than gm ever thought about.

-Scott

 

[EfrainlCazares]

Completely unnecessary, IMHO. Normal operating temperatures are 190-200°.

I've done this on multiple occasions, original transmission still shifts perfectly with 180k on it. 20k miles of heavy towing, including the Rockies and the Eisenhower Tunnel.

I f I were you, I'd be a lot more concerned about the rear axle than the transmission. Have you checked its temperature while towing? Have you checked your weights while towing? I'd be willing to bet it's either a) getting really hot, or b) overloaded, or both.

I'd upgrade the rear diff cover to one with cooling fins. I towed lots of heavy stuff with my half-ton Suburban, and it still has the original transmission at 250k miles, but it's on rear end number 4.

Damn....looks like mine when I hauled my TT two hours. The transmission temp was at 231 and the engine temp at 225. GM of course told me that it was normal temp for AWD Denali, so I called the GM shop I bought it from, asked about an additional transmission cooler voiding lifetime drive train warranty and I was told it was ok, as long as I didn't do anything to cause breakdown of transmission. Now when hauling even up hill my temp is only 195 max. I also got a three core radiator as welll

 

[Sean James]

If you drive in sub-zero area's of the Country you can overcool the trans fluid and even the engine oil. At -20F. a lot of vehicles wont even start without engine heaters or kept in a garage. I don't want to change to 0W oil and back in 5 different vehicles every winter and back to 5W-20 every Spring, it gets expensive for cars that share maybe 50-100 miles a week. I don't imagine N Kentucky gets sub-0 temps so I wouldn't worry about a trans bypass.

 

[Doubeleive]

Heat kills pretty much anything this is a widely accepted fact
having had numerous transmission problems in the past generally thru my own fault I was concerned when I purchased my 2012 awd denali and it consistently had transmission temps in the 200+deg range having come from a 5.3 4wd that would consistently hovering at 180 deg, without towing anything and just driving. I added a deeper transmission pan which gives it 2qt's extra to help cool and added the trucool 40k, my goal was to get the temps down to 160 consistently. doing this met and exceeded that goal.

 

[97audia4]

Added a truecool 40k before towing my race trailer this summer.

90 degrees and humid through NC in August and at highway and around town temps were 170 to 180.

Trailer is 7.5x 16 with extra height weighing around 5,000 lbs. I'm in PA and it was 0 a few times this winter and even with that warming up for 5 minutes and my 20 minute ride to work the temp always reached at least 100 degrees so I would not add a thermo bypass

 

[kaleburditt]

So original post was about the trucool 40k. I have one. And I tow. A lot. I too have been up Eisenhower tunnel. I believe it was 12 below in breckinridge the last time I did it a few months ago. Here's my review. Get it. Be done with it.

Now for technicals. Liquid to liquid is better than air to liquid. So run from the trans to the radiator then to the tru cool. Your trans fluid will normally be within a few degrees of engine. I didnt like the thermostat being at 180. So I didnt install it initially. So I have constant cooling. What was it at 12 below? 100. That's like a 80 degree drop. What does it run normally? About 130 tops when the motor is running 190 ish. That's 60 degrees. How about engine at 235 and its 105 outside pulling in 5th up a hill out of lockup. Well then it gets warm. Like 190 to 210 tops. But hey that's only 10 degrees over the crappy thermostat. And it cools down quick unlike without.

The transmission self test features can only be done when its warm. Which according to the program is 95 degrees. So yeah your good. Get it. Be done with it.