Yesterday we drove about 400 miles through mountains with a total GVWR of 20,000. Trans temps were fine all day. This morning it's -40 and we've let the truck warm up and driven maybe a mile and the trans temp is at 170. I still have about 3500 miles to go and could really use some opinions on this one. Thanks.

 

Feel the lines on the trans cooler to see if they are warm. If not, the bypass may be open and the fluid is not going through the coolers.

 

Sounds good. Will the bypass close and allow it to go through the cooler at a set temp? Or os it something I'll need to manually fix?

 

Also, if the lines are warm and fluid is running through the cooler, then any other thoughts?

 

What were your temps before?

 

130 to 140

 

I'm thinking Rick has got you figured out. I think the bypass will close off to help warm up the tranny and open at a
Certain temp so if you felt the lines and they were warm it has probly started circulating by then. But definatley keep
An eye on it and let us know how your trip turns out!

 

Lines are cold. Is there a fix for the valve?

 

Thats not how the bypass works. If the cooler plugs up, then bypass will open and the fluid will go to the back of the trans and into the pan. Not heat activated.

EDIT: If the temp didn't get over 220*, then you are good to go.

 

Temps have dropped to 115ish and holding....will keep u guys posted on the trip.

 

wow, 3900 mile move....where are you headed?? good luck with the trans

 

Thought I read that somewhere. Wrong again! See I told you Rick had you covered!

 

Trans has been holding solid temps for the past 2 days. Moving from Alaska to New Mexico. It must have just been the -40 that my truck didn't like that morning. We're in Fort Nelson, British Columbia, Canada now. Pulled some steep grades up and down all day today and trans never got over 130.

 

At -40 non-synthetic ATF will gel in the air to oil cooler. It will get think enough that it stops flowing. Now the bypass will open so that fluid is still sent to the rear of the trans where it is used for lubrication.

 

-40??? Holy Cow that's cold.

It looks like you are OK and Mark's explanation is very informative.