P0740 is torque converter clutch malfunction.
Quote from another forum:
"If the only code you have is P0740 (which is for a faulty lock up system in the transmission) you might be able to fix it for less money. First what you can do is replace the lockup control solenoid valve assembly (you most likely have to get this part from a dealer!) It is probably going to be cheaper than a whole tranny, but it might not correct the problem and if after replacing that part and the code p0740 returns then it means there is an internal failure in the transmission you are going to need to replace the tranny."