While waiting for a response from someone who has had this code...
The first thing I would do is install a gauge or programmer that can display torque converter clutch slippage.
I have not had the code, and the slippage when the TC is locked hovers around zero.
Here is some information regarding the code you have.
P0740-TCC OUT OF RANGE
Theory of Operation
When in 2nd, 3rd, or 4th gear, the Torque Converter Clutch (TCC) can be locked or partially locked when certain conditions are met. The TCC piston is electronically modulated by increasing the duty cycle of the LR/TCC solenoid until the torque converter slip difference (difference between engine and turbine speed) is within 60 rpm. Then the LR/TCC solenoid is fully energized (FEMCC / 100% duty cycle). Torque converter slip is monitored in FEMCC to ensure adequate clutch capacity. The transmission will attempt normal EMCC operation (not in limp-in) even after the MIL is illuminated. MIL will illuminate after 5 minutes of accumulated slip in FEMCC.
The Torque Converter Clutch (TCC) is in FEMCC or PEMCC, Transmission temperature is hot, Engine temperature is greater than 38° C or 100° F, Transmission Input Speed greater than engine speed, TPS less than 30°, and brake not applied.
The TCC is modulated by controlling the duty cycle of the L/R Solenoid until the difference between the Engine rpm and the Transmission Input Speed rpm or duty cycle is within a desired range. The DTC is set after the period of 10 seconds and 3 occurrences of either: FEMCC - with slip greater than 100 rpm or PEMCC - duty cycle greater than 85%.
RELATED L/R SOLENOID OR PRESSURE SWITCH DTCS PRESENT
2008 Unlimited Rubicon Automatic