Going cooler crazy!

[intheburbs]

I've had my 2008 2500 for 13 years. Lots of great memories made in it - our family vacations are always road trips. We're getting ready for another 3-week Epic Family Road Trip, and I've been doing a lot of preventive maintenance - plastic heater hose fitting, hose replacement, fluid changes, etc. She has 275k miles, so I know things are wearing out. The upcoming trip will be ~6000 miles and multiple Continental Divide passes including the Eisenhower Tunnel (11,100').

One of the things I noticed was the A/C condenser was pretty rough-looking - lots of smashed fins, plugged slots, etc. I figure this is also restricting airflow. Rock Auto had new condensers for $100, so I bought one.

My buddy works at a top-notch shop so I gave it to him. I was also having him drop the transmission pan to replace the filter and do a full fluid replacement, and we were talking about my towing the behemoth and trans temps. I told him how I've hit 240° at times towing in the Rockies. So he talked me into the Mishimoto trans cooler -because it uses the same fittings as the factory cooler.

Then we noticed the power steering cooler looked rough. Knowing that system also acts as my brake booster, I decided to replace that as well.

I plan to have this truck until I die, so I'm doing projects with a vision for the long-term.

For the 6L90 detractors, it's the original transmission, never dropped the pan in 13 years and 170k miles, and my buddy said, "very little dusting on the magnet." The fluid has been replaced 5 times while I've owned it, but never did a pan drop/filter replacement.

ETA 8/10/26: First real-world driving test. Took a two-hour drive to Grand Rapids for a romantic weekend with my bride.

Good: Whereas in the past the trans would get up to "operating temperature" at about 100° over ambient, on this road trip (not towing, cruising 80-85 mph) the trans got up to about 55° over ambient, settling in around 140-145°. Running at least 40° cooler.
Bad: The A/C is behaving like the evaporator is icing up. Friday, outbound to GR, was insanely humid, and as we drove the air volume out of the vents continued to decrease over a period of about 30 minutes. Finally, I turned off the compressor (leaving the system on and blowing) and the air stayed cold for a good 5-10 minutes. Over this time the airflow returned to what it should be. Did it again on the drive home yesterday, albeit not quite as bad.

Next update will be an AAR for my big trip - 6000 miles, pulling the behemoth, Yellowstone/Bryce, Eisenhower Tunnel and Powder River Pass.



Pics:

Before

After:

The reason why:

Edit to add:

 

[Marky Dissod]

For 6L90 detractors, it's the original 6L90, never dropped the pan in 13 years and 170k miles, and my buddy said, "very little dusting on the magnet."
ATF has been replaced 5 times while I've owned it, but never did a pan drop/filter replacement.

So, you replaced the ATF every 34,000 miles if not more often?
Never been a detractor of changing ATF on the severe service schedule ('severe' service schedule should be the normal service schedule ... in my opinion ...)

 

[intheburbs]

So, you replaced the ATF every 34,000 miles if not more often?
Never been a detractor of changing ATF on the severe service schedule ('severe' service schedule should be the normal service schedule ... in my opinion ...)

My shortest interval was 22,000. That was when I took two trips to the Rockies, and smoked the transmission multiple times on each trip. Like 235°-243° on the DIC display as I was climbing the Continental Divide passes. The fluid was brown and smelling a little burned, so I changed it.

The five times includes when I bought it, at 106k on the odo, in 2013 when I changed all fluids. This current change makes six:

106811 (just purchased)
152727
189567
232002
254269
272411 (current)

This is almost my all-time high score of 243°. It's hard to get a clear pic of the DIC display, because it flickers like a television, ~25-30 hz and the camera doesn't always catch the full display. Previous trip up the "Ike Guantlet," the western approach to the Eisenhower Tunnel (elev 11,100 ft). 14 miles of 7% grades. and the thin air not only reduces cooling, but reduces engine power by about 30%.

 

[solli5pack]

Did you notice any difference on how the A.C. performed after the swap? Looks awesome!

 

[randeez]

the best time to upgrade the trans cooler is before you put 100k towing miles on it, i sposed the next best time is now
props for actually changing the fluid often after seeing those temps
cooler looks very similar to the popular transcool 40k, but even easier install

 

[89Suburban]

My question is can those factory hard lines be added to a vehicle without factory equipped external cooler when installing that aftermarket cooler?

Is there a diagram showing the differences of the factory hardlines and routing between the two?

 

[opfor2]

I've had my 2008 2500 for 13 years. Lots of great memories made in it - our family vacations are always road trips. We're getting ready for another 3-week Epic Family Road Trip, and I've been doing a lot of preventive maintenance - plastic heater hose fitting, hose replacement, fluid changes, etc. She has 275k miles, so I know things are wearing out. The upcoming trip will be ~6000 miles and multiple Continental Divide passes including the Eisenhower Tunnel (11,100').

One of the things I noticed was the A/C condenser was pretty rough-looking - lots of smashed fins, plugged slots, etc. I figure this is also restricting airflow. Rock Auto had new condensers for $100, so I bought one.

My buddy works at a top-notch shop so I gave it to him. I was also having him drop the transmission pan to replace the filter and do a full fluid replacement, and we were talking about my towing the behemoth and trans temps. I told him how I've hit 240° at times towing in the Rockies. So he talked me into the Mishimoto trans cooler -because it uses the same fittings as the factory cooler.

Then we noticed the power steering cooler looked rough. Knowing that system also acts as my brake booster, I decided to replace that as well.

I plan to have this truck until I die, so I'm doing projects with a vision for the long-term.

For the 6L90 detractors, it's the original transmission, never dropped the pan in 13 years and 170k miles, and my buddy said, "very little dusting on the magnet." The fluid has been replaced 5 times while I've owned it, but never did a pan drop/filter replacement.

Pics:

Before
View attachment 490237

After:

The reason why:
View attachment 490238


Edit to add:
View attachment 490241

I like this cooler.. Maybe a future project?

 

[randeez]

My question is can those factory hard lines be added to a vehicle without factory equipped external cooler when installing that aftermarket cooler?

Is there a diagram showing the differences of the factory hardlines and routing between the two?

one of the lines should be the same, transmission to lower radiator cooler
from top of radiator to this cooler in
out from this cooler back to the transmission

GM GENUINE 25999420
GM GENUINE 15779543

 

[intheburbs]

Did you notice any difference on how the A.C. performed after the swap? Looks awesome!

Thanks. Haven't gotten a ton of wheel time with it yet, just picked it back up yesterday. My buddy's shop had it for over a month.

But it was 92° when I picked it up, and I had it cranked on max blower speed and recirculate, and it was putting out some seriously cool air.

the best time to upgrade the trans cooler is before you put 100k towing miles on it, i sposed the next best time is now
props for actually changing the fluid often after seeing those temps
cooler looks very similar to the popular transcool 40k, but even easier install

As I mentioned, I was always a "stock is good enough" proponent and had no intention of upgrading the cooler. Another friend of mine worked for GM and was actually on the validation team for the 6L80/90 back in 2005-2006. I started asking him questions about towing and temperatures and what I'd been seeing. He pretty much poo-pooed it and said, "We did a lot worse during validation."

Additionally, the fact that I've never dropped the pan, nor cleaned the magnet, nor changed the filter, in my time owning the truck and my mechanic buddy said, "very little dusting on the magnet." I'll take that as a very good sign of TLC.

 

[Marky Dissod]

ATF has been replaced 5 times while I've owned it, but never did a pan drop/filter replacement.

So, you replaced the ATF every 34,000 miles if not more often?
Never been a detractor of changing ATF on the severe service schedule ('severe' service schedule should be the normal service schedule ... in my opinion ...)

My shortest interval was 22,000. That was when I took two trips to the Rockies, and smoked the transmission multiple times on each trip.
Like 235°F-243°F on the DIC as I was climbing the Continental Divide passes. ATF was brown and smelling a little burned, so I changed it.

Firmly believe that GM put the ATF temp sensor where it was easy to place, instead of where ATF is hottest when working / playing hard.
When your ATF was reported @ 243F, would not be surprised if some portion of the ATF was 265F-270F, which would explain the off color & smell.

The five times includes when I bought it, at 106k on the odo, in 2013 when I changed all fluids. This current change makes six:
106811 (just purchased)
152727
189567
232002
254269
272411 (current)

May your 6L90 live long & prosper.

 

[strutaeng]

Sweet!

 

[2011burbLTZ]

You should have upgraded the radiator and fans after seeing your engine temps while the trans was at 241.

 

[intheburbs]

You should have upgraded the radiator and fans after seeing your engine temps while the trans was at 241.

Upgrade the fans to what?

 

[Marky Dissod]

Upgrade the fans to what?

Do you have RPO K5L?
Someone correct me if I got the RPO wrong.

 

[intheburbs]

Do you have RPO K5L?
Someone correct me if I got the RPO wrong.

K5L wasn't an option for the 2500s. All of them had KC4 (External/heavy-duty engine oil cooler) and KNP (Heavy-duty / auxiliary transmission oil cooler (air-to-oil)).

And the radiator core is already an upgrade over half-ton SUVs, as it's the same as the GMT900 2500 HD pickups.

 

[Marky Dissod]

K5L wasn't a 2500 option. All of them had KC4 (External/heavy-duty engine oil cooler) and KNP (Heavy-duty / auxiliary transmission oil cooler (air-to-oil)).
And the radiator core is already an upgrade over half-ton SUVs, as it's the same as the GMT900 2500 HD pickups.

Asking out of genuine curiosity to learn here:
1. KC4, is this a heat exchanger for motor oil integrated with the radiator's driver side tank?
Or is it a separate air-to-oil cooler?
If I'm not mistaken, 1500s & suvs use a heat exchanger integrated with the radiator's driver side tank for motor oil.
2. KNP ... this question is formatted similarly to the first.
If I'm not mistaken, 1500s & suvs use BOTH a heat exchanger integrated with the radiator's driver side tank for ATF, AND a separate ATF air-to-oil cooler in series.

Basically I'm wondering if it's possible to install a 2500 radiator into a Tahoe. I'm always trying to improve on GM OE, with GM OE, if you get my meaning.

 

[PG01]

Careful Marky, he may bite your head off…

 

[donjetman]

Asking out of genuine curiosity to learn here:
1. KC4, is this a heat exchanger for motor oil integrated with the radiator's driver side tank?
Or is it a separate air-to-oil cooler?
If I'm not mistaken, 1500s & suvs use a heat exchanger integrated with the radiator's driver side tank for motor oil.
2. KNP ... this question is formatted similarly to the first.
If I'm not mistaken, 1500s & suvs use BOTH a heat exchanger integrated with the radiator's driver side tank for ATF, AND a separate ATF air-to-oil cooler in series.

Our 07 Yukon Denali has what I consider the inadequate factory KNP external trans cooler. From tranny, to pass side radiator heat exchanger, to a small cooler in front of radiator and condenser, then back to tranny. IF I towed I would remove it and install something like a Tru-Cool Max w/cold wx bypass pt# LPD4739.

 

[intheburbs]

Asking out of genuine curiosity to learn here:
1. KC4, is this a heat exchanger for motor oil integrated with the radiator's driver side tank?
Or is it a separate air-to-oil cooler?
If I'm not mistaken, 1500s & suvs use a heat exchanger integrated with the radiator's driver side tank for motor oil.
2. KNP ... this question is formatted similarly to the first.
If I'm not mistaken, 1500s & suvs use BOTH a heat exchanger integrated with the radiator's driver side tank for ATF, AND a separate ATF air-to-oil cooler in series.

Basically I'm wondering if it's possible to install a 2500 radiator into a Tahoe. I'm always trying to improve on GM OE, with GM OE, if you get my meaning.

To (poorly) answer your questions...
1) I don't know
2) I was under the impression the only interface with the transmission fluid is the small radiator in the front of the stack. Both of my trucks, the Suburban and Sierra Denali, have the exact same transmission cooler.

I don't see why a 2500 radiator wouldn't fit into a Tahoe. It's the same body/front clip. I guess it comes down to the supports. I've never torn down the stack to look closely at everything; I've just torn off the front clip to replace headlights.

 

[PG01]

So, having just done the rad on my tahoe with the hd tow pkg:
trans cooler lines go: trans to rad out of rad to cooler out of cooler back to trans on the pass side. (99% sure on routing)
Oil cooler: comes from above oil filter to drivers side rad back to oil filter.
As far as the stack goes the fans just bolt up top to rad support and clip to rad at the bottom and the rad sits directly (with pads) on the rad support at the bottom and there are just 2 bolts up top to the rad support.
Width wise (driver to passenger) should be same as and 1500 or 2500 and thickness of radiator wouldn’t matter because there is 2’ between the fans and water pump pulley, crank pulley. etc (obviously exaggerating)

Ps: i have k5l and kc4