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Trans coolers

Bobmontana
Explorer
Explorer
While towing our 3000lb travel trailer with our 2011 Yukon xl 1500 5.3 litre I found that it does ok for the most part but the transmission did get up to 220 degrees going over Macdonald pass in Montana. We were down to 45mph and 3000 rpm just as we crested over and the trans gauge touched 220. Has anyone replaced the stock cooler with a larger one that is a OEM ? I don't like the idea of scabbing in a cooler attatched too the radiator and just rubber hose clamped to the lines. Than you for your time.
19 REPLIES 19

Wyldfire
Explorer
Explorer
Grit dog wrote:
Roger10378 wrote:
I like to see trans temperature reach 220 occasionally. Water condenses in the trans oil and needs to be boiled out occasionally.


I like your theory, but in 30+ years of driving and exclusively wrenching on all my own stuff and some for others, I have never come across that issue in any vehicle new or old save for maybe one that was severely neglected.
And if it was even remotely an issue, I donโ€™t believe most auto trans mfgs would design them where they ideally Never reach anywhere near that high of oil temperature.


You are way behind the times. Fords new transmissions have used increased temperatures to make them more fuel efficient. Normal operating Temps are 200 to 259. See:

https://youtu.be/C0iKcag-wr8

time2roll
Nomad
Nomad
I call normal and ordinary. Leave the engineered system in place. Cutting into the lines and adding a bunch of hoses and cooler from Pep Boys just adds additional fail points.

Bobmontana
Explorer
Explorer
Thank you all for your replies!

jerem0621
Explorer II
Explorer II
I added a Hayden trans cooler to my 2011 Tahoe. We pulled a 7200 lb TT and I never saw temps over 200 after that.

Thanks,

Jerem
TV-2022 Silverado 2WD
TT - Zinger 270BH
WD Hitch- HaulMaster 1,000 lb Round Bar
Dual Friction bar sway control

Itโ€™s Kind of Fun to do the Impossible
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BenK
Explorer
Explorer
The flaw in thinking additional external aux ATF coolers will impede the engine coolant radiator...it does not or enough to reduce the main radiators function

If so, then remove the AC condenser (the tube fin radiator in front of the engine coolant radiator) and the OEM external aux ATF cooler, which are all in front of the engine coolant radiator. That will remove all blockages this line of thinking would require for proper functioning

Sizing by the thermal dynamic systems designer/engineer has the main coolant radiator good for the maximum conditions spelled out in the specifications. Plus whatever MAXIMUM margin management allowed (always too low to suit me...like lots of margin, but bean counter's penny-pinching wins).

That sizing then has a throttle to no over cool the coolant and is the thermostat/etc.

IMO, if the OP wants to keep their ATF cooler, sure thing, add either a larger plate ATF cooler in place of the OEM...or add another plate type cooler plumbed either in series or parallel to the OEM cooler. Key to keep the OEM routing that has the ATF go through the OEM radiator, which will keep the ATF at proper temps in extremely cold climate conditions

Fastidiousness is key in working with ATF plumbing.
-Ben Picture of my rig
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1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

LITEPHIL
Explorer
Explorer
By the way, Most of my towing is up to the Arizona High country and often when I leave the Phoenix area in the summertime, it's well above 100 degrees out and sometimes in the 110-115 range and the hills are 6-7% grades and EVERY truck I have had including a Dodge 5.9 and a Duramax 6.6, transmissions have gotten to 220-225 on the climbs and the coolant temps would go 3/4 on the temp gauge.
The only time I would worry is if it was stop and go. But I do keep an eye on things.
2022 Chevy Silverado RST Duramax NHT
1954 Chevy 3100 Carryall 4x4
2008 Salem T23FBL
04 FXDL Harley

LITEPHIL
Explorer
Explorer
Everything sounds normal. 220 on a steep grade and towing is perfect and 3000 rpm at 45 mph is great. none issue.
2022 Chevy Silverado RST Duramax NHT
1954 Chevy 3100 Carryall 4x4
2008 Salem T23FBL
04 FXDL Harley

Bionic_Man
Explorer
Explorer
As others stated, I wouldnโ€™t even blink an eye at 220.

Speaking from experience, I had a 6.2 pulling much more weight, concerned about trans temps (which were much higher) and I changed to a larger tranny cooler which blocked more of the radiator which caused significantly higher engine temps.

Moral of the story. I wouldnโ€™t change anything if I were you.
2012 RAM 3500 Laramie Longhorn DRW CC 4x4 Max Tow, Cummins HO, 60 gallon RDS aux fuel tank, Reese 18k Elite hitch
2003 Dodge Ram 3500 QC SB 4x4 Cummins HO NV5600 with Smarty JR, Jacobs EB (sold)
2002 Gulf Stream Sea Hawk 29FRB with Honda EV6010

C_Schomer
Explorer
Explorer
My trans was hitting ~220 so I put a cooler under the floorboard and got it under 160 without putting that heat in front of the radiator.. Craig
2012 Dodge 3500 DRW CCLB 4wd, custom hauler bed.
2008 Sunnybrook Titan 30 RKFS Morryde and Disc brakes
WILL ROGERS NEVER MET JOE BIDEN!

Microlite_Mike
Explorer
Explorer
A couple things to note re: McDonald Pass. Average grade is just under 6% but there is one significant stretch that's 10%.

If the OP is "doing OK" most of the time I'd just gear down and keep moving if back on that road again.
"Knowledge is realizing that the street is one-way, wisdom is looking both directions anyway."


~ Albert Einstein

BarabooBob
Explorer III
Explorer III
If I were towing with a V8 going up grades in the mountains I shift down to keep the rpm's up. This results in more HP and lower tranny temps. Your V8 probably puts out just over 200 HP at 3000 rpm's. Kick it down, rev it up a bit and you are making close to 400 HP and will top grades at whatever speed you want and the tranny will be cooler.
Bob & Dawn Married 34 years
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Retired

Microlite_Mike
Explorer
Explorer
Ideal operating temps for modern Automatic Transmissions are from 170F - 225F.

I wouldn't worry about 220F for a short time, especially when climbing a steep grade where temps tend to rise when pulling hard.

One important step when towing is to change fluids more often. Every fluid, engine oil, Atf, Engine Coolant, and Power Steering fluid take a beating under the heat created by towing.

On my vehicle I change Oil every 5K and ATF/PS/Coolant every 50k. So far my 19 year old truck (2004 Titan) tows my 6,000 trailer up anything I've encountered in the West.
"Knowledge is realizing that the street is one-way, wisdom is looking both directions anyway."


~ Albert Einstein

Grit_dog
Navigator
Navigator
8 miles at 8% under a load will clean the cobwebs out of most vehicles.
What temps do you run, say on a 4-6% at highway speeds?
Also, 3000rpms is nothing for a LS motor. If you dropped it another gear, the trans would run a bit cooler.
Now if youโ€™re pulling steep grades frequently which you may be, presume a 6 speed suburban has an external cooler, Iโ€™d consider a larger cooler. Or another option, deep pan for more fluid capacity and a bit of cooling with a finned pan may yield similar results.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5โ€ turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold

Grit_dog
Navigator
Navigator
Roger10378 wrote:
I like to see trans temperature reach 220 occasionally. Water condenses in the trans oil and needs to be boiled out occasionally.


I like your theory, but in 30+ years of driving and exclusively wrenching on all my own stuff and some for others, I have never come across that issue in any vehicle new or old save for maybe one that was severely neglected.
And if it was even remotely an issue, I donโ€™t believe most auto trans mfgs would design them where they ideally Never reach anywhere near that high of oil temperature.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5โ€ turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold