I don't think it matters. It didn't appear to affect mine when I installed it. This tread brings up a question though. I did not by pass the radiator but as I think about it now I probably am defeating the purpose of the cooler. I ran the lines from the tranny to the cooler and from the cooler to the radiator then back to the tranny. My thought now is if I wanted to lower the temp in the tranny and I ran the lines from the cooler to the radiator didn't I just cancel out the effect of the cooler? Wouldn't it be best, if I want to use both, to go to the radiator first then the cooler then back to the tranny? Now that you made me think about it I think I have mine *** backward.