Error code P0740

If i were you i would first try the TCC (Torque Converter Clutch) solenoid, also check the wiring and make sure that it's not your problem.
If that doesn't work then it might be the TCM (Transmission Control Module.)

I took it to the dealer and told them the code I pulled. They had trhe car for a day and they say that Hyundai says to replace the transaxle with that code. Sounds fishy to me. It's funny that since I've got it back from the dealer it drives fine now. Humm???