P0700 Transmission Control System Malfunction
This code indicates that the EATX (Transmission controller) has an active fault and has illuminated the MIL via a BUS message.
P0740 Torque Converter Clutch Circuit Malfuction
Torque Con Clutch - No RPM Drop at Lockup
Relationship between engine and vehicle speeds indicated failure of torque convertor clutch lock-up system (TCC/PTU sol).
Are these the same codes as before (you didn't give the exact numbers)? If they are, then the shop likely looked at those codes and decided you needed a new torque converter, because the error code implies the t/c is not locking up when commanded. I'm skeptical that you got a tranny rebuild for $600, but thinking instead they just dropped the tranny and stuck on new torque converter. You mentioned they replaced a solenoid too? That would probably be solenoid #3, which could also cause the problem.
So I see a few possibilities:
- The shop installed the wrong torque converter
- The shop didn't actually do anything to the tranny and instead figured out the starting problem and charged you $600 anyway.
- The problem is not and never was the torque converter, but maybe a wiring problem or a problem inside the tranny.
- Bad TCU
I think you need to go back to the shop and ask them to honor their warranty, because they sure didn't fix the problem.