Right around 64 MPH is when the F37 transmission tune done by Chrysler shifts into 5th and locks up the torque converter. They also flashed a "torque reduction" feature(?) into the engine controler to eliminate this that happened on the original as from the factory tunes did at about 59 MPH.
For the most part Chrysler's F37 tunes eliminated the "shudder" problem but left us with enemic CRD's
Your GDE "full torque" ECO tune has much less torque reduction programming in over drive gears that both 4th and 5th are but you have more then
I have the GDE "full torque tune" and both the pre and post TCM (transmission) controllers and with the updated Chrysler "euro" torque converter intended for the 07 and up CRD's that were not available in the US.
Here's a couple of things you can try. Check the transmission fluid level, change the transmission fluid and filters, and finally update your torque converter to a better one like the Sun Coast one.