hello to all,

I have 02 HD with 4r100 with factory cooler. Which line is the supply line from the tranny to the cooler?

Thanks,
Tony

 

The line attached to the front of the transmission goes to the cooler. The cooler returns fluid to the rear of the transmission.

 

You can also start the truck up put the emergency break on, then put it in gear. Then the line that get hot first is coming from the tranny, the cool one is the return line. ( Your tranny must be cold for this to work). Both will eventually get hot so you have to be pretty quick.

Steve