Transmission cooling issues

[werewilfs]

So I did some installation and am reporting results for future googlers here;

I added a 19 Row setrab cooler and kept the "Superior" radiator cooling in line after this cooler and it made no difference to my temps. Still climbing up to 200F fairly easily. BTU rating for this cooler was something like 15,000 - 27,000 depending on airflow etc.

So I added a second identical cooler and removed the radiator from being involved at all. After first 1 hour test drive temps did not go above 150F.

So either removing the radiator, or adding the second cooler did the trick. Probably a bit of both. Engine temp is solid 180F all the time.

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Next up is to remove the old hardline in full just so I know it is all serviceable in the future.

I also noticed this plate on my transmission - but can't fully decipher what it says. I was just curious as my transmission has a temp sender in it which many others seem to say they don't have. I assume maybe these earlier versions had them and it was removed in later versions maybe.

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Interestingly, there is such a thing as "too cold" for transmission fluid and apparently it runs through the radiator to "warm it up" as much as it does to cool it off. If you never run the motorhome in the winter, you're likely just fine running it outside of the engine radiator as you have it set currently. If you do take it out in cold temps, you may have issues.

 

[pvfjr]

Was this switch pitch already in your transmission or did you have to swap out the transmission with a model that had this already? This wasn't standard on GMC Motorhomes as I understand it?

Still very much learning a lot of this stuff. I didn't know I needed external cooling until recently!

It's from the 66/67 Toronado transmissions. You're correct, it was not a standard feature on the GMC motorhomes.

 

[LQQKatJon]

Interestingly, there is such a thing as "too cold" for transmission fluid and apparently it runs through the radiator to "warm it up" as much as it does to cool it off. If you never run the motorhome in the winter, you're likely just fine running it outside of the engine radiator as you have it set currently. If you do take it out in cold temps, you may have issues.

My tranny guy says the same thing. No one complains about a tranny running too cool. I am sure there is some amount of moisture that could be in the tranny, but with 3+ gallons of ATF I am not sure there is any concern.

Ideally running series with the radiator is best. But many times that radiator cooler is compromised. Mine probably runs too cool and I do use mine in the winter a couple times. It still gets to the same warm temp as summer even at 0 degrees….

I have not yet blown this tranny up!

 

[pvfjr]

Derale also makes transmission line thermostats to help keep things operating warm enough.

The idea of never allowing engine coolant and transmission fluid to mix, even in the event of a failure, is a desirable one. I've seen that happen on other vehicles. It's a bad situation.

 

[jampants]

Derale also makes transmission line thermostats to help keep things operating warm enough.

The idea of never allowing engine coolant and transmission fluid to mix, even in the event of a failure, is a desirable one. I've seen that happen on other vehicles. It's a bad situation.

Yes this is my thought also. If there was an issue in the radiator which I would never know until its too late its going to be a bad situation.

I'm probably not planning on going anywhere if its less than 40-50F outside so suspect I'll be ok.

 

[sailor man]

Was this switch pitch already in your transmission or did you have to swap out the transmission with a model that had this already? This wasn't standard on GMC Motorhomes as I understand it?

Still very much learning a lot of this stuff. I didn't know I needed external cooling until recently!

The original switch pitch torque converter was installed in a number of GM luxury cars around the time the the GMC Motorhomes were built. I don't think that it was installed in the GMC Motorhome.

At the time, the switch pitch was controlled by the throttle linkage near the carb. I think. When I got the coach, the switch pitch was already installed but was controlled by a toggle switch that basically down shifted the tranny.

The seller said that he did not use it often because he used more gasoline.

When I read about Bruce's "black Box" solution, I bought one and had Cliff Golby install it.
Bruce said that if there were any problems, he would reprogram it.