Need advice for flushing transmission factory cooler lines that connect to radiator

[Burnsy]

Hello all. I have a 2001 ranger v6 3.0 flex fuel automatic. I want to flush the tranny cooler lines but have no experience doing it ...im handy enough just never done it...i have a few questions. ..first, I have 3 metal lines.......there is an external cooler also but I'm not concerned w that as ive already flushed it......back to the 3 metal lines......one comes from the tranny to the top of radiator(supply feed i assume), one comes out of bottom of rad and goes to external cooler(continue of supply feed i assume), the 3rd line comes out of external cooler and goes back to the tranny(return line I assume)..........do I need to unscrew the lines at the tranny ? Will the tranny lose fluid there when / if i do that ? Will it be a lot? Do I drain tranny first ? What about the lines at the radiator? Unhook them both ? Here's my idea, is this feesible ?....undo the supply line at the tranny,then undo the supply line at the EXternal cooler and blow air or flush it all the way thru, which would include the air/flush going thru the top and then bottom rad lines ( that I would leave connected to the rad) and then exiting thru the open external cooler line...........then for the return metal line, it will be disconnected from the external cooler and also disconnected at the tranny. I would blow air/flush thru it and then I'm done....?........ So I never remove the metal lines from the radiator, only removed from the tranny housing and from my external cooler...logistically seems doable and seems fairly easy, can I do this this way ? Removing the lines from the rad makes me a little nervous never done it,/special fittings/way to remove them?.....is it any easier removing the lines where they go into the tranny vs where they go into the rad ? ? Different fittings/ method ? I'm thinking the removal at the tranny is different/easier than the fittings at the rad, that's why I have the idea i do lol thanks, sorry for the long letter just trying to cover everything

 

[RonD]

There are just 2 trans cooler lines
And there is one VENT metal line that comes from back top of transmission loops up bell housing and back down to end near drivers side shifter
Picture here of the Vent hose from drivers side: https://www.therangerstation.com/tech_library/images/transmission/4R55E_driver_side.JPG
Trans fluid heats up and cools down so there has to be an "air vent" at the top of trans to allow for expansion and contraction as fluid heats and cools

The 2 trans cooler lines are on passenger side just behind bellhousing, seen here: https://www.therangerstation.com/tech_library/images/transmission/4R55E_passenger_side.JPG

The lower port is the OUT to cooler
Upper port is IN from cooler(return)


As for cleaning the cooler and lines you can build a connector and use a rubber hose and funnel and allow gravity to run clean fluid thru the cooler and out the lower line then do the same for upper hose
Both line disconnected from trans of course

You can also buy "trans cooler flush", comes with connector and has fluid flush liquid in compressed air can to force fluid thru the lines and cooler