Transmission cooler Lines?

[DEEPWOODS]

Does anyone know if the top or bottom line is the return on this transmission cooler or does it matter ?

 

[phred]

Keith I don’t think it matters which one is which on the cooler.

 

[Steve83]

The one connected to the front of the trans is hot fluid out; rear is cooled fluid in.

 

[Yeller]

Phred is right, doesn’t matter. Some will argue that it does, I have seen no evidence.

 

[Broncobowsher]

That one I don't think it matters.

There are a few times where it can matter. Header tank style coolers can trap an air bubble in the top of the cooler in a top down flow pattern. Those are the ones you want to flow bottom up, so the air bubble will be flushed out of the header tank.