Automatic Transmission won't shift out of 2nd gear???

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OK! One of the transmission computer/solenoids had to be replaced and everything was working fine. Then! After driving it 25-30 miles it said those terrible words, "SERVICE ENGINE SOON". I completed a scan and code "P0744 Torque converter clutch circuit intermittent" appeared. Any suggestions? Also while you're thinking about that, here's another question. I've been around cars all my life (63) when all you needed was a spark and fuel and a motor would run. 2nd question. When the vehicle has been setting for at least 24 hours completely cold without being driven, coolant come from some where in the front of the engine. I drive it to my mechanic he pressure test the system, no leaks. Drive it back home let it set 24 hours coolant leak again. With it cold, I've checked every hoses (about 6) and the water pump and can't find any kind of leak only where it's dripping off and there are no hoses or water jackets in the area. If it can go wrong, it will happen to me. :-( Thanks in advance.