which is the return line...

[small pederson]

on a 94 aw4? im putting on a cooler, but i cant start up my rig right now to figure out which is warmer.

[martin]

If you have the lines hook up to the radiator then I know which ones are which. If you are talking at the transmission I am at a loss.

The line going into the upper connection on the radiator is the "hot" line. The line coming out the lower fitting of the trans cooling in the radiator is the "cold" line.

I installed the Mopar Aux cooler and they connect it to the bottom fitting on the radiator. The ATF flows through the aux cooler then into the rubber line crimped to the hard line connected to the transmission.

[Matthew Currie]

There ought to be a FAQ on this, it comes up so often.

Adding to Martin's post, on the transmission the outlet is the one that is further forward, and higher. The return is further back.

[KarmirXJ]

if you have a aftermarket cooler, doesnt really matter where you plug the lines in, they are universal.