Is my transmission bad?

What needs to come out the transmission? What internal failure could be?

I took my car to a mechanic and he checked the car and he put it in the machine and all the engine and transmission codes appeared and he said that my transmission might not be the problem but the computer. How true can that be? I also noticed once my car is running it wont change shifts. Can the computer control all that or this mechanic is fishy?

I had to take 2004 Mercury Sable and I took it in today for the same reasons minus the loud noise. The hesitation and not shifting gears when accelerating. My diagnostic test said to be misfires. The mechanic said it could be anything from a new computer or something as minor as a tuneup. Any luck with your car since?

Well I took it to a mechanic and he said it wasn't the transmission and he changed the coil and cables and the car worked for a month and a half then did it again. (I didn't mentioned that my car had the engine light on for a while prior to all this)so after he changed what he changed even the engine light was gone for a few weeks then it came up again and a month after the engine light came up again the car started doing all I mentioned in my other questions. I took it back like a week or 2 ago and he said that it was the mass air flow sensor. I haven't change it yet because he took the cables back out and spray cleaned everything and the car is running good except that the engine light is back on. So before it does it again I will change my mass air flow sensor which I checked online what the symptoms are for a defective mass airflow sensor and they are very very similar to my car symptoms.