This means that the TC is not engaging.
The PCM will attempt to engage TC 5 times and it monitors the TCCMACT = Actual slip across the TCC, measured in RPM ,PID. It looks for this to drop below 100 rpm(it will actually go as low as 20 in a total lock up.If it can not achieve this after 5 attempts it will set the P1744 code. There are alot of things that could cause this on this tranny but usually if you follow this TSB(technical service bulletin) from Ford it will correct the concern. However unless you are doing the work yourself it is usually not a whole lot of difference in price between this repair and installing a reman unit which has a lot more warranty(ford's is 3yr or 100K miles on a reman) as opposed to 12month or 12K miles for repairing yours.
Here is a copy of the TSB
Article 98-6-5 is being republished in its entirety to update the model years and to identify additional contributors to the DTC's being set
Torque converter clutch not engaging when commanded and/or Diagnostic Trouble Codes (DTC) P0741 or P1744 stored in memory
Use a scan tool (NGS/WDS) to monitor PID's to help determine steps to take for service. Refer to the following Diagnostic Procedure for details.
The torque converter clutch may not engage if one or more of the following conditions exist:
Use a scan tool (NGS/WDS) to monitor the following PID's: