transmission rpm shot up on the highway, now revs and stays in 1 gear, po1740

This code is related to the torqure converter clutch but this should not prevent shifting. When you say it revs in 1st gear, does the truck move and just wont shift out of 1st? Or does it rev up like its in neutral?

I have had this problem on my Cummins very often. Should be the mostly the same transmission. My transmission will never shift out of first gear.....There is a sensor on the back of the transmission called the speed output sensor. If it goes out it won't shift because the transmission computer won't read any speed coming from the transmission......it can also be the two wires running to the sensor. A green and blue. Lots of times people will hit something and rip the wires out of the sensor... just check the wires and if they are clean and plugged into the sensor, replace the sensor.