Keeping coolant and transmission temps under control when towing in the summer heat

[RooTBeeRthe1st]

The folks here are GOOD at helping spend your money.

Hahaha
That's one of those things I absolutely don't need any help with.

 

[Geotrash]

Update after test drive: Took the Yukon out for a little highway cruise to get it up to temperature this evening. Ambient air temp was 70ºF. The transmission temperature gradually climbed and held steady around 175º on the highway after 20 minutes or so. Then getting off the highway and going through traffic, the temp crept up to 185º. I stopped in a parking lot to check the cooler fan and it wasn't running yet. It didn't kick on until the indicated transmission temp was between 190º and 195ºF (stopped again to check when it was 194ºF), but it quickly stopped the rise and started bringing it back down. I shut the engine off and after a minute or so the fan stopped with the temp back down around 182ºF indicated.

Curious what those of you running this cooler are finding with it, where it keeps your temp with and without towing, and whether the fan brings your temp back down when towing up a grade effectively. Thanks for your thoughts.

 

[thompsoj22]

Update after test drive: Took the Yukon out for a little highway cruise to get it up to temperature this evening. Ambient air temp was 70ºF. The transmission temperature gradually climbed and held steady around 175º on the highway after 20 minutes or so. Then getting off the highway and going through traffic, the temp crept up to 185º. I stopped in a parking lot to check the cooler fan and it wasn't running yet. It didn't kick on until the indicated transmission temp was between 190º and 195ºF (stopped again to check when it was 194ºF), but it quickly stopped the rise and started bringing it back down. I shut the engine off and after a minute or so the fan stopped with the temp back down around 182ºF indicated.

Curious what those of you running this cooler are finding with it, where it keeps your temp with and without towing, and whether the fan brings your temp back down when towing up a grade effectively. Thanks for your thoughts.

Where did you tap power? Ign off fan off right? Those temps seem correct if you are still using the radiator "pre heater". How effective were you at getting the max ram air through the lower grill? The trans oil enters the bottom of the radiator "heater", Exit's the top "heated" and flows through the DERALE and back to the trans so temps will allways be influenced by radiator coolant. I have seen "stable" trans temps as low as 114 on 50 degree 70 mph freeway cruising, Which is "ram air" overcoming the radiator heater. My average temps on 80 degree oat are 155 degree's at 70 mph. Stop and go freeway traffic at 80 oat are same as yours approx 175 degrees once the fan comes on. Im going to eliminate the radiator from the circuit this summer and see how much of a difference it will make.

 

[Foggy]

Just for the record: I kept the trans cooler circuit in the radiator.. So it goes
into the radiator - then to the derale cooler - then back to trans
In my short test drives, I'll get everything good and hot... Trans temp gets to
about 172* and stabilizes with suburban driving... IF I turn on the fan, the temp after a couple minutes will drop down to about 160* ish..
I haven't towed yet though... But I figure 10*-15* degree drop by turning on
the fan will keep me happy when towing

 

[03_GMC]

Fans are still programmed to come on at the factory temps. I bought the 700w fan motor for the drivers side, along with the correct fan blade, and will install both this weekend.

Thanks for offering some good ideas.

I highly recommend getting the fans programmed to come on with a higher duty cycle at lower temps. The factory programming is shit.


Sent from my iPhone using Tapatalk

 

[thompsoj22]

A couple more showing the mounting and wiring from the bottom. I have 2 more straps that will attach to the bolts that hold the skid plate on.

View attachment 277637
View attachment 277638

Cant explain the "no power" fuel pump fuse location but given that the fan will run for just a few minutes after shutdown as you have explained in another post id give your install an A+! That looks profesional and will add reliability to your vehicle. As i have commented previously, In order to see the true capabilities of the DERALE i think it should be used as a standalone and not use the factory radiator heater. Another member has installed the same cooler without the radiator so we will know soon enough what the difference would be. Great work!

 

[Geotrash]

Where did you tap power? Ign off fan off right? Those temps seem correct if you are still using the radiator "pre heater". How effective were you at getting the max ram air through the lower grill? The trans oil enters the bottom of the radiator "heater", Exit's the top "heated" and flows through the DERALE and back to the trans so temps will allways be influenced by radiator coolant. I have seen "stable" trans temps as low as 114 on 50 degree 70 mph freeway cruising, Which is "ram air" overcoming the radiator heater. My average temps on 80 degree oat are 155 degree's at 70 mph. Stop and go freeway traffic at 80 oat are same as yours approx 175 degrees once the fan comes on. Im going to eliminate the radiator from the circuit this summer and see how much of a difference it will make.

Thank you for the details on your numbers, John. I plumbed it so that coolant flows from the transmission directly to the Derale and then back to the transmission. I have a front license plate in the way of getting direct ram air on the cooler, so the next step will be to fabricate some deflectors from aluminum sheet to direct the ram air coming in on either side of the license plate through the cooler instead of beside it, and rivet them in place. The numbers I'm getting make sense to me though because the transmission temperature sensor sits in the valve body, so it's plausible that it would be 10-15º cooler by the time it gets to the thermal switch on the cooler's inlet port through 6' of mostly aluminum line. Thus, if the switch activates the fan at 180º it makes sense that at the valve body the temp would be 190º+ by the time the fan comes on.

I wired it into fuse #34 (S/Roof - Roof Beacon Relay (TRW), Sun- roof Module (CF5)) which is an 'always on' circuit typically used by police vehicles for the light bar, because I was in a hurry to get it tested and running (state inspection scheduled for this morning), but can easily put it in a different circuit. The fan will likely only run for a minute or two when cooling down anyway, but I would rather have it on a circuit that's switched on with the ignition. Problem is that every switched circuit I tried had no power unless its accompanying relay was also switched on. For example, the rear window defogger fuse wouldn't power up until I turned the rear defogger on. I have the up-fitters manual though so will figure out a better circuit.

One additional step I can take is to wire in an override switch that will allow me to turn the fan on before the temp gets to 194º indicated, or find a thermo switch that activates at 170º. I'll try these after I get the ram air directed toward the cooler better.

All of this said though, I like that this setup is running warmer than the Trucool 40K. With that cooler, I rarely saw transmission temps reach the minimum temp that GM specifies for continuous operation (150ºF). GM is very clear that it's possible to overcool a transmission with oil-to-air coolers, so as long as I can keep my trans temp above that and below 210ºF or so when towing on the hills or sitting in traffic, then I'll be fine with that.

 

[Geotrash]

Cant explain the "no power" fuel pump fuse location but given that the fan will run for just a few minutes after shutdown as you have explained in another post id give your install an A+! That looks profesional and will add reliability to your vehicle. As i have commented previously, In order to see the true capabilities of the DERALE i think it should be used as a standalone and not use the factory radiator heater. Another member has installed the same cooler without the radiator so we will know soon enough what the difference would be. Great work!

Thank you! Your ideas and photos helped tremendously - can't thank you enough for posting them.

 

[Geotrash]

Just for the record: I kept the trans cooler circuit in the radiator.. So it goes
into the radiator - then to the derale cooler - then back to trans
In my short test drives, I'll get everything good and hot... Trans temp gets to
about 172* and stabilizes with suburban driving... IF I turn on the fan, the temp after a couple minutes will drop down to about 160* ish..
I haven't towed yet though... But I figure 10*-15* degree drop by turning on
the fan will keep me happy when towing

Thanks for clarifying, Tom. I misread your photos. Sorry about that and thanks for clarifying and sharing your numbers. I like your idea of wiring in an override switch, and may do that.

 

[Geotrash]

I highly recommend getting the fans programmed to come on with a higher duty cycle at lower temps. The factory programming is shit.

That's a good idea and will likely do that, but I have a hunch that my engine cooling problem will be solved now that there isn't a massive transmission cooler in front of it. Time for an HP Tuners setup.