As I have been instructed by one of the great GT Guys, when using a transaxle cooler, the typical filler plug is not used. Instead, get some nice clear plastic hose, 1/2 inch, I cannot recall, a couple of feet long. Remove the speedometer sensor carefully, as not to damage the re-usable O-ring. Once the fluid has been drained and the screen cleaned out and the drain plugs snugged back up, follow the book as to the number of transaxle fluid quarts to put back in, PLUS ONE MORE. Most of the fluid from the transaxle cooler drains out during a normal change, and the filler plug above the drain plug will not allow for this required extra quart to be added. I know my tubing extends to the rear tire and that is the point where I allow gravity and a bit of squezzing to refill the transaxle.
Hope this helps.
Pete S.