Trans coolers

[Bobmontana]

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.

[Wyldfire]

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 don’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]

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]

Thank you all for your replies!

[jerem0621]

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

[BenK]

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.

[LITEPHIL]

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.

[LITEPHIL]

Everything sounds normal. 220 on a steep grade and towing is perfect and 3000 rpm at 45 mph is great. none issue.

[Bionic_Man]

As others stated, I wouldn’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 wouldn’t change anything if I were you.

[C_Schomer]

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

[Microlite_Mike]

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.

[BarabooBob]

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.

[Microlite_Mike]

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.

[Grit_dog]

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 you’re pulling steep grades frequently which you may be, presume a 6 speed suburban has an external cooler, I’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.

[Grit_dog]

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 don’t believe most auto trans mfgs would design them where they ideally Never reach anywhere near that high of oil temperature.