It's been -35C here or colder overnight, and -27 or colder days, for about 2 weeks....so quit yer bitchin'. Haha.

How is your aux cooler hooked up? I was told by a trans guy to retain the factory cooler/exchanger and put the aux cooler in the circuit before the factory one, as the factory one will warm cold trans fluid. A front cover still helps though..

Another thing to remember is that the PCM will also lock out O/D when the battery temp is below...-20F? That's off the top of my head, might be wrong. There is a battery temp sensor located in the bottom of the battery tray. I know some remove it and wrap it around the upper rad hose to keep it warm, but I prefer to keep it where it belongs as the compy varies charge rate based on this sensor too. So instead, I stuffed a bunch of rags underneath the battery tray, and wraped the battery and put plastic over the outside of it in an effort to insulate it (the battery will produce some heat when charging, trying to retain that heat) and it did seem to have at least a small effect. I'm guessing most of you won't have frequent enough issues with this to bother with such things though.....

98BlueSport, the compy doesn't light up the O/D off light when it's too cold. It will still come on when you push the button, just won't go into O/D. The light comes on and stays on when the trans gets too hot....there's a second stage of "too hot" that brings up the trans overtemp light. You might have an issue with a temp sensor there.

 

I don't have an auxiliary cooler, yet when it hits -20C (seems like that temp is the point where it happens), I lose OD. The only cooler is the in-rad one. Seems kind of odd that my engine will run at normal temps at -20C yet the transmission won't be warm enough to run in OD.

 

You would not find me out and in my truck at -20C. Saw temps like that when I worked in Sweden years ago......no more, thank you.

The low temp effects the physical properties of the tranny fluid, which alters its ability to allow clutches to engave properly.