Mitsubishi Magna ES '05 (F4A5 tiptr auto)sedan trans locks in 3rd help

Magna05Aus

please help me scotty, I have a mazda ES Sedan (4 speed auto with tiptronic, F5A4 transmission which was just replaced), the car runs fine for the first few minutes then locks into 3rd gear until the engine is turned off and back on, it also shows me as going 20km above my actual speed.
I have tried using all of my friend's OBD2 scanners but it will only connect to the ABS and 2 sensors. I cannot get a code from ANY of them and I've been told I'm looking at at least 750 dollars just to MAYBE get it fixed.
I am an veteran and on a pension for a broken back and neck, but I am also an old hat in the programming and system analyst/repair areas, (unemployed and on a pension atm) and think it has to be either the speed sensor or the TCM and or ECU.
Please help I live in a regional area and now the ball joint on the front drivers side is gone and I'm up for big money (for me anyway). Is there ANYTHING AT ALL you can recommend off the top of your head please? I have tried the short test but the light blinks constantly.
KM on the clock 165,000km,
just had a 2nd hand transmission which came from the almost exact same model car (it was the 05 model before the ES, and also F4A5).
When driving under 5kmph all is well for about 5 minutes, then you hear and feel a clunk, and the drive light starts flashing and you can feel that it's either in 3rd or in between 3rd and 4th. The scanner modules (all of them except the mk3 mitsubishi model, which I cannot get access to) show that the ECU, TCM, etc. etc. etc. will not connect, like they are just not there, I have tried to get the ECU to respond using terminal mode but I can't even get it to give me a diagnostic connection to the onboard computer. Curiously only the Dashboard computer, ABS , and Immobilizer even ping as there, but 0 comms. I have literally ONE place in the entire REGION of Australia (Goldfields Coolgardie area), where I live, (its basically the desert), about 100km from me that thinks they can help
but it will cost me 200km of fuel and $140 per hour for them to even look at it. I can't afford that in my wildest dreams right now, when they want rego, insurance, license fees AND a 14 year olf 4,000 fine all at the same time. I really, REALLY need some help here, I have a lot of exp in TTL(binary transistor to transistor logic), EEPROM based systems, FPGA systems, microcontroller programming, SOC (system on chip) and more, I know Hexadecimal and Octal numbering systems and know ASM and C, if it is a programming problem I would be immensely grateful if someone can help me to interface with the system and find out the problem. Sincerely, and Faithfully, Jason Ezekiel