The cooler is for the hydraulic oil, not the transmission oil. Freightlioner had a number of cooling issues with the Freightliner XC chassis and the Cummins 400 ISL. Too much heat for too small a radiator is what it boils down to. They did a few recalls to fix the airflow around it with baffles, etc and they also replaced the Dexron 3 fluid with heavier 15W-40 motor oil so that the hydraulic fan motor would spoin faster once the oil got hot (the lighter Dexron would thin out and the motor would lose RPM).
Now they find out that the heavier motor oil causes the hydraulic oil cooler to rupture because there's too much pressure in it. So this recall fix is basically to fix the last recall fix.
It is not related to your transmission cooler problems.
Note that this recall is only for the 400 ISL powered chassis with side radiator. The smaller Cats with rear radiators don't have that problem.