I have spoken with Jeep in Norway and they are aware of the problem. They made an inquiry about my question and directed it to the factory that built Jeep for Europe. The factory is located in Gratz in Austria. They wouldn't listen, and answered that the 3.1 TD with the 44RE transmission was programmed to engage the lock-up at 122 km per hour. Therefor ALL WJ 3.1 TD acts the same. They won't create new software even though jeep work shops from all over europe have asked these questions since the car was new in 1999.
I have created a group at facebook to try to get hold of enough people across europe or maybe the whole world. This might turn into a signature campaign. If we can get enough members, maybe the factory has to listen to us.
When the lock-up don't engage, the car uses about 0,1 to 0,2 desilitres more per 10km, it polutes much more, and the transmission gets warmer and wears more rapid. And when you ad the fact that Jeep probably have received hundreds, if not thousands og questions about why every jeep transmission engage the lock-up at 75 km/h BUT the 3.1 TD one can wonder why they haven't created a new software for this transmission. They did it with the 45RFE to turn it into the 5-45RFE transmission.
So if you own a 3.1TD join my group, and maybe we can persuade Jeep to help us with new software for this transmission.
Please promote this Facebook group in you own country. I have so limited knowledge of all the national and local jeep clubs.