How to Determine Which Line is the Return Line for Installing Supplemental Transmission Cooler

Question:

I am going to order and install a transmission cooler on my 2001 Chevy Silverado 1500 4.8L. The installation seems pretty straight forward, however it appears in one of your diagrams that you attached the cooler to the return line going back to the transmission. My question is how can I tell which line to tap into, how do I know which line is the hot coming from the tranny and which is the cool line returning to the tranny ? Thanks

asked by: Jerry

Expert Reply:

In order to tell which transmission fluid line is the return line leaving the factory cooler of a vehicle like your 2001 Chevy Silverado you want to start with your vehicle cold. Start it up and put it in drive and brake torque it (apply brakes and rev the engine), for about 10 seconds or so, put vehicle back in park, and turn engine off.

Now quickly go out and feel both transmission lines. The cooler of the two is the return line and the one to use for installing the # D13035.

expert reply by: Jameson C