Quote Originally Posted by 2nasti View Post
I have seen it run every which way. Here is why I suggest the way I did, yes the other works too.

Like you said, the trans fluid will try to equal the coolant of the radiator, which should be close to ideal trans fluid temps. If run the way I suggested, even if the aux cooler before the rad makes the fluid too cool (say 140*?) the radiator should bring it back up before sending it to the trans. If the trans fluid was so hot the aux cooler before rad could not get it low enough, say 225*?, the radiator should bring it down further before sending it back to the trans. Seems like either way the fluid should be under control and not too cold. The trans fluid will try to equal the coolant in the radiator, which is less than the reading on your dash. I don't see a downside unless there is an extreme trans overheating issue, and I think the aux after the radiator would then show its superior cooling ability.

The only downside I see with the aux after the radiator is if the fluid leaving the radiator is ideal, it is about to be cooled further, possibly below ideal. Like I said, I have seen them both ways and neither had issues. I just like the idea of the radiator having the final say, as it will either cool down fluid further if its hotter than the coolant in the radiator, or raise the cold atf closer the radiator temp but never higher. The aux cooler can only reduce the temp further.

Try the aux cooler after the radiator, if you don't like the temp range, try it the before the radiator. You can recheck it in the summer too.
Great points and discussion! After reading this, I think either way could work well.