Hi thank you for your question hope this helps.
P1740 code (TCC or O/D Solenoid Performance)
There is a TSB (Technical Service Bulletin) issued for this.
A TSB is a bulletin sent out by the factory for repair problems that are the fault of design of the system. Any problem such as yours will be repaired at the factory / dealers expense.
TSB 21-11-00 This bulletin applies to vehicles equipped with the 46RE transmission built be for AUGUST 01, 2000
This bulletin involves the replacement of the transmission pressure boost valve cover plate.
Passable symptoms: The customer may complain of a Malfunction Indicator Lamp (MIL) illumination. Upon further analysis, it is determined that the MIL is caused by Diagnostic Trouble Code (DTC) PI740 -Torque Converter Clutch (TCC) or Overdrive Solenoid Performance. Other than the MIL, the customer may not notice any other condition with the transmission. This condition may be caused by an intermittent and momentary TCC disengagement condition. The transmission valve body pressure boost valve cover plate has been revised with a larger size orifice hole to address this condition.
Hope this helps
You do not need an extended warranty.
You will need to tack it in to the dealer to have them look it over and determine if this falls under the factory. when they find it out that yes it falls under the TSB # XXXXX they may try to give you the run around but stand your ground. this is not a hard repair it should tack around 1 two 2 hours to do.