How hot is your transmission with an aftermarket cooler?

Wondering what transmission cooler peoples have, and how much it drops the temp of your transmission.

Stock, after a 40 minute drive, mine tops at 196, in the burning up the fluid territory.

digdug18 said:

Wondering what transmission cooler peoples have, and how much it drops the temp of your transmission.

Stock, after a 40 minute drive, mine tops at 196, in the burning up the fluid territory.

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What are you driving and what year is it and does it have K5L (Enhanced Cooling Package)?

Constant temps of under 200 is fine, hitting 230 for short big uphill climbs while towing is also normal.
Higher the ambient temps the higher the trans temps.

In Florida's 92 degree heat, wind variable at 3 knots, truck at speed on cruise for over 20 minutes the temp runs 156 degrees at 76 mph turning about 1900 rpms.

Same speed and profile, similar winds, temperature 82 degrees the transmission temperature runs 151 degrees.

You asked for modified but due to the underwhelming response I thought I'd help your post in any way I could. Mine is stock with K5L.

196 is fine.

digdug18 said:

Wondering what transmission cooler peoples have, and how much it drops the temp of your transmission.

Stock, after a 40 minute drive, mine tops at 196, in the burning up the fluid territory.

Click to expand...

I think I’m about 10 degrees lower on average with my bigger cooler. I kind of expected more. The only reason I went bigger was because I was pushing that 230 mark towing across I80 in PA. That’s a brutal route.
Personally, I wouldn’t worry unless you start towing a big trailer.

swathdiver said:

What are you driving and what year is it and does it have K5L (Enhanced Cooling Package)?

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How would you tell if you have the K5l package?

97audia4 said:

How would you tell if you have the K5l package?

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RPO sheet . It will have engine oil cooler in radiator, external transmission cooler in front, larger radiator, more powerful fans and taller gears.

I just had Derale plate/fin transmission cooler (https://www.etrailer.com/Transmission-Coolers/Derale/D13503.html) installed last week on my 2017 Yukon as we are heading on an 8 week trip through the Rockies in August and wanted to be sure I wouldn't overheat in the mountains. We're towing 19 foot 5000 lb (loaded) camper, so not pushing the 6300 lb max towing limit.

I did some testing before/after the cooler install for comparison. Before the cooler the transmission would run at around 185 on the flat while towing and hit 210 up a 3 mile 6 degree rise, both at 65 mph. Without towing it was 180 on the flat. After the cooler was installed the same test gets 185 towing on the flat and 195 up the same mile 6 deg rise. Without towing the temperature sits at 180 on the flat. The dealer tells me that the thermal valve on the transmission doesn't open until 195 and that seems to match my experience (never got above 195 up the hill with the cooler, below 195 the valve isn't open and the cooler doesn't come into play).

The installation was a bit ugly. The transmission cooling lines on mine go into the A/C condenser (not the radiator) and you have to take the grill/bumper cover off to get to it. Mechanic took about 5 hours for the install and charged me $550 including parts.

FYI, the dealer told me that the aftermarket cooler would void the transmission warranty but given our trip through the Rockies I thought it was still a reasonable cost risk mitigation as the transmission is not likely to fail until after the warranty expires and the cooler waon't contribute to any such failure in any case. The Yukon only has only 10K miles on it and we plan to do a lot of towing during it's life.

If I weren't going through the Rockies I would have gone without the cooler.

On my old '88 GMC C2500, I had a built transmission. I installed a 'Setrab' brand cooler... ( about 300 bucks)

Worth it......

Stop looking at the transmission temp.... it will drive you nuts.

digdug18 said:

Wondering what transmission cooler peoples have, and how much it drops the temp of your transmission.

Stock, after a 40 minute drive, mine tops at 196, in the burning up the fluid territory.

Click to expand...

When I first used my Yukon XL Denali to haul a 30ft about an hour from where I live, transmission jumped to 230-35 and engine jumped to 225...I didn't like it....I called GM and told me it was normal temp, especially for a AWD. I called dealership and talked to the shop manager and he told me adding a two or three core radiator and an additional transmission cooler wouldn't void lifetime warranty, it would actually help, as long as I didn't cause any fluid leaks to make it fail. I added a bigger cooler on top what came with it and a three core radiator. The temp on hwy now is about 154 in summer, 190 while hauling on a central TX raod. I kept the same temp thermostat, but I can tell it helps me Denali a lot!