I installed a tru-cool 4379 because I'm fixin' to buy a 32' travel trailer and add a chip.

My tranny temps now hover between 125-150 (I haven't towed anything since the install). I didn't think I needed the by-pass valve cause I live in Houston down near the gulf and we rarely see freezing temps.

Now I'm beginning to worry about the temps being too low.

 

Craig64,

Don't sweat the low temps.... anything above 100 F is ok for the low end.

What were you running before the cooler install?

 

Thanks.

I was running up to 170 pre cooler install not towing anything.

 

i am sure you will be fine with those numbers... if you do happen to have a cool morning sometime, just start her up and let her warm up for a few minutes before you leave..

 

The tranny oil goes from the transmission to the lower tank of the radiator, where the oil is cooled by heat exchange with the radiator water. Then it goes to a cooler in front of the radiator where it is cooled by air flow. When your truck is warmed up, the thermostat controls the water temperature from the engine to about 180 F, which goes to the top of the radiator. As it passes down it cools to maybe 150 F or so. If the tranny oil is much colder than that, there is a bypass line on the tranny so the oil is just recirculated to the transmission instead of the radiator until it warms up. The bottom line: The tranny oil will never be too cold; it will be recirculated in the tranny till it warms up, and then when it goes to the radiator it can't get much below 150 F or so because the radiator water will warm it. In the winter it might be cooled well below 150 F by the second water-to-air cooler, but then that will cause the bypass line to recirculate the oil back to the tranny to keep it warm. Thats the way its supposed to work, so just keep an eye on the aftermarket tranny temperature guage to see that it does. Keep in mind that it takes quite a while for the whole thing to warm up first thing in the morning - like miles and miles.
Warren

 

for those of us who live in the great white north, we have the tru-cools installed to deal with the summer heat, and then we cover them up in the winter... but if you plow a little snow like i do, it's nice to be able to uncover that cooler when you do... plowing snow really heats up a tranny...!