Get That Transmission Cooler!

Buckwheat · June 4, 2017

Hi Folks,

This is kind of an update on my towing questions and recent experiences while pulling about 6500 lbs of camper and other "stuff" with it.

About the second week on April I was pulling our camper with a 2002, 2500HD, 6.0 4x4, 4L80E transmission... the outdoor temp was upper 70's low 80's that day. and while towing with the factory cooler it briefly hit 225 degrees...no long hill climbs...just typical driving...some flats and some mild to moderate hills. and the transmission temp mostly stayed around the upper 180's to 200 degrees.

So after that temp climb I was inspired to install a large "Long" brand cooler and do a filter and transmission fluid pan only change and ( some extra fluid was also added to make up the difference of the larger cooler).

Well after driving about 700 miles with camper in tow and outside temps in the upper 80's, it never got to over 163 degrees and mostly stayed around 150 degrees.

LOL knowing the transmission was not slowly roasting itself, really dropped my stress level down to having an enjoyable drive while in tow. While I never went over 65 mph, I pretty much stayed around 55-60mph....if you plan on doing some towing this summer, do yourself a favor and add a larger transmission cooler...your heart will thank you for not heaping a bunch of unwanted stress on it!

Thanks for all your help on this folks!

Chris · June 4, 2017

Go bigger if you live in a desert area. Mine is huge. I'm almost afraid to leave California in the winter. My grand will barely get to 110 in the winter here

Raptordude · June 4, 2017

Can a transmission be too cool?

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sdeeter19555 · June 4, 2017

Can a transmission be too cool?

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No...

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Formulabruce · June 4, 2017

Can a transmission be too cool?

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Yes it CAN be too cool. I was running a 160 T stat here and had some slipping and long delay engage, long delay downshifts in the winter when it was cold ( below freezing for a few days or longer) I know this used a ton more fuel as well. I went to a much bigger trans cooler and back to stock T stat and all is well

Colossus · June 5, 2017

I believe that a tranny can be too cool to do any good. Like engine oil, If the fluid is too cold it will be thick and not providing the best lubricating.

sdeeter19555 · June 5, 2017

Wow, then how do these trucks manage to survive in northern Alaska and Canada? I have cold started mine at -25 degrees, drop it in drive and go...

I put 200k miles on my one truck a few years ago, it wouldn't break 65 degrees some days when it was cold...transmission ran just fine. Same with this 2012, it won't break 100 degrees all winter unless it gets above 30 degrees outside.

If cold temps cause issues with your trans, then you have underlying issues. Period.

The only argument I ever heard that had any merit was that a trans that ran too cold won't drive off condensation, but if that was a problem; the ATF would look like a strawberry milkshake.

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Raptordude · June 5, 2017

That's what I heard. I heard condensation doesn't burn off until like 190, which seems hot to me. GM says operating temp for 4l80 is between 175 and 225 (I think that's around what they say) but that seems awfully hot to me.

If anything my truck seems to shift smoother when it's cold. There's nothing wrong with it, it shifts fine while hot too, just seems a little smoother when cold

I've never seen temps over 180 with my factory trans cooler, but my grandpa used it for years to pull a 5th wheel camper so I'm sure it's no stranger to heat

Thought about putting a larger cooler in, but given that I've never seen over 180, (typically run around 165-170 in the summer) I'm wondering if a bigger cooler would keep it too cold

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Buckwheat · June 5, 2017

Hi Folks,

I cant tell a difference in shifting before or after adding that big cooler. I have personally seen an automatic transmission delay in shifting here in South Carolina on some cold mornings....but thats a whole diffrent vehicle, so I could be comparing apples to TV sets. However, the cooler mfg also had a version which had a temp bypass, which would bypass much of the cooler until it reached a certain temp....since Im in South Carolina and its not too often for me to see a delay in shifting due to cold weather, I opted not to get it.

When I reached 225 while towing that camper, it was not on the instrument cluster I got that reading from...it was a glow-shift gage I added and was using the test port location for the temperature probe....so Im assuming that there was also a delay or slow to get a reading in real time with the probe in the test port....If I had installed it in the return line I probably would have had a "quicker" reading from it.

Formulabruce · June 6, 2017

Wow, then how do these trucks manage to survive in northern Alaska and Canada? I have cold started mine at -25 degrees, drop it in drive and go...

I put 200k miles on my one truck a few years ago, it wouldn't break 65 degrees some days when it was cold...transmission ran just fine. Same with this 2012, it won't break 100 degrees all winter unless it gets above 30 degrees outside.

If cold temps cause issues with your trans, then you have underlying issues. Period.

The only argument I ever heard that had any merit was that a trans that ran too cold won't drive off condensation, but if that was a problem; the ATF would look like a strawberry milkshake.

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All I said was that cold ( below operating temp) can and does affect a transmission. With a Stock T stat ( fast warm up and tranny at 100 degrees, its all good. I t have used my truck in extreme cold in the US and Canada, but running a 160 T stat for towing was the wrong answer in the winter, even though the LQ did run in closed loop.

Formulabruce · June 6, 2017

Hi Folks,

I cant tell a difference in shifting before or after adding that big cooler. I have personally seen an automatic transmission delay in shifting here in South Carolina on some cold mornings....but thats a whole diffrent vehicle, so I could be comparing apples to TV sets. However, the cooler mfg also had a version which had a temp bypass, which would bypass much of the cooler until it reached a certain temp....since Im in South Carolina and its not too often for me to see a delay in shifting due to cold weather, I opted not to get it.

When I reached 225 while towing that camper, it was not on the instrument cluster I got that reading from...it was a glow-shift gage I added and was using the test port location for the temperature probe....so Im assuming that there was also a delay or slow to get a reading in real time with the probe in the test port....If I had installed it in the return line I probably would have had a "quicker" reading from it.

Cool will not change the way the trans "feels" if using the correct thermostat. All it does is allow for more heat transfer out of the fluid when its getting a bit hot. This is a biggie, and will greatly improve trans life

sdeeter19555 · June 6, 2017

Cool will not change the way the trans "feels" if using the correct thermostat. All it does is allow for more heat transfer out of the fluid when its getting a bit hot. This is a biggie, and will greatly improve trans life

Let's ponder this for a moment...colder temps will yield a slightly more viscous ATF (read: thicker, more cushion and/or more resistance to flow), and a change in tolerances (steel contracts different than aluminum when cold); so why couldn't there be a different feel?

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Formulabruce · June 6, 2017

Let's ponder this for a moment...colder temps will yield a slightly more viscous ATF (read: thicker, more cushion and/or more resistance to flow), and a change in tolerances (steel contracts different than aluminum when cold); so why couldn't there be a different feel?

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There is increased pressure and a "slower feel" , I mentioned slower shifts, etc. Not sure how many would actually "feel" it depending on drive habits and the actual temp

dasimmon · June 6, 2017

a must for towing

mookdoc6 · June 6, 2017

On my specific 8L90 with the so called HP for cold temperature shifting performance I can say that it's FEELS much different at 40-50f start up to 110f in the garage from winter to summer in the desert.....This vehicle in particular is very noticeable compared to previous vehicles?