I heard that the best way to install a trans cooler is to let the fluid go threw the radiator then into the trans cooler and back to the trans. Does anyone know what the return line is the top one or the bottom one and how is the best way to install the cooler?

 

The top line on a 700/4L60E is the return line. You'll want to run your bottom line (at the transmission) through your radiator, then out to the external cooler, and then back to the transmissions top line.

Frank
CPT

 

Thank you vary much Frank.