wondering which line is the to and from flow direction top or bottom which line takes fluid to radiator and which returns the fluid to the tranny please help

2001 4.3l 4dr

 

Next time you take it for a drive feel the lines, the return will be the cooler of the 2.

 

if you think about it, the transmission lines that go in and out of the radiator are not actually cooling anything in these s-10's and blazers. they are HEATING them up. if you have been in a bigger truck with a real trans temp gauge then you would notice that the trans only runs about 110 or so when you dont have a load. the trans lines in the s-10's and blazers are run through the radiator. the radiator is how hot? about 200 degrees F. the so called "cooler" for the trans really just heats up the fluid since they are the same temp as the radiator that they are running to.
so to answer your question, take one of them off and have someone start the car. if fluid comes out of the trans tube then you know which is which, if it comes out the radiator, then you still know which is which. dont let it run long because you are using the pump in the trans to figure this out. then you can bypass the stock "cooler" all together and run an external one that will actually do something.

good luck.

 

Fluids to the radiator including the oil and transmission lines travel to the top the radiator so the flow is with gravity down to the bottom for the return. It is fairly obvious that it's not going to be set up to push against gravity. To replace the transmission cooler lines you pretty much have to remove the transmission for access.
I agree with the transmission fluid actually being heated up as it goes through the "cooler". What up with that thinking?

 

I'm pretty sure the OP got it figured out by now, but logic would dictate that the fluid would flow from the hot part of the radiator (top) to the cool part (bottom). It has nothing to do with gravity. And what the "cooler" does is keep the transmission temperature consistent. When it's cold, it warms it up and when it's hot, it cools it.