Finding Transmission Return Line on 2001 Ford F250

Updated 12/19/2020 | Published 12/18/2020

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Derale Radiator Adapter Fittings for Ford, Lincoln and Mercury

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Derale Series 7000 Tube-Fin Transmission Cooler Kit w/ Hose Barb Inlets - Class IV - Standard

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Question:

I’m replacing the factory transmission cooler with a heavy duty cooler on 2001 Ford F250. Problem: there are two lines. Which is the supply and which is the return?

asked by: Daniel Q

Expert Reply:

This is pretty easy. The line to the cooler will be warmer than the return line. To determine which is which, start the engine when it's cold. Put your foot on the brake, and shift into D for about 10-15 seconds, keeping your foot on the brake. Put the transmission back in part and shut off the truck. Feel the transmission lines or use an IR thermometer like # TM48FR. The cooler of the two lines is the return line, which is the one you want to tap the cooler into. You'll also need the # D13025 fittings you'd looked at.

I'll link you to an article with additional information about transmission coolers. I'll also link you to a install video showing a # D13105 cooler being installed on a 1999 F-350.

expert reply by: Mike L