How to Identify the Transmission Cooler Oil Return Line On a 2008 Jeep Wrangler

Updated 10/25/2011 | Published 10/23/2011

Question:

Which line out of the trans is the cooler return line? I purchased a trans cooler part #13503. Thanks

asked by: Dave W

Expert Reply:

The best way to determine which line on a transmission cooler is the return line from the radiator is to use the following procedure:

1. Start engine while engine is cold
2. Place transmission shift lever in drive for no more than 10 seconds.
3. Stop engine and remove keys
4. Identify the oil return line by feeling both oil lines. The coolest line is the oil return line.

On an aftermarket transmission cooler like the Derale cooler, part # D13503, the ports are not input specific or output specific. It is not directional so you can choose either port for either function. You will want to choose the inlet or outlet port location by what will make your installation easier.

I am including a link to a FAQ page on transmission coolers.

expert reply by: Jeff D