Mitsubishi Repair: 2001 mitz trans problem, junked cars, bad trans

Question
2001 mitz my transmission went out i got another trany for it everything was the same except it didn't have a speed sensor.so i split the case and put the gear from my bad Trans into this Trans so id have the senser.i have a problem it goes into safe mode.i took it to auto zone they put there tool on it and it said i had a problem with the solenoids 123.my question is do i have to put all the sensors and solenoids from my old Trans into this one?/ the guy from auto zone says i need the tcm from the car i got the Trans out of but that wouldn't do me no good if it didn't have a speed sensor right?he also said i might have to have the computer erased and reprogrammed and could cost $800.00 dollars thats crazy what else can i do it all should be the same if i change all the sensor from the old to this one right? thanks G

Answer
Henry: I think your problems is with the sensors not the computer, you could reset the computer in the car, if the transmission you put into your car is the right one for your car, year, model and engine size. You did not try to put in something with more power or from some other car then what you have. It could be that the wiring is off, broken or forgot to hook up something, the computer is picking up a problem with the transmission and so putting the transmission into that safe mode. I think I would go ahead and replace all the sensors that the computer picked as problems. Sometimes the plug for the sensors get old and don't plug the sensors in as they should. You might be checking them. But also before you go and have the computer reprogramed or whatever the AutoZone guy came up with and check with the dealership. I can not say I have heard of that one before, but then I only work in a small shop. We do replace transmissions from junked cars into other cars, don't mess with the computers and as far as I know never had a problem with that. Unless you got one of those older cars with the bad computers. Still before you spend all that money on the computer, check with the dealership on that. God bless: Linda