Chrysler Repair: 2001 TOWN & COUNTRY SPEEDOMETER GOING HAYWIRE, speedometer needle, 4 digit numbers

Question
I have a 2001 town & country 3.8. Just bought this van and the speedometer goes haywire. When you take your foot off the break the speedometer needle goes from one side to the other and car starts jerking like it will shut off. I have changed both sensors input and output.Took it to a transmission place to see if any codes come up. They told me alot of codes came out but wouldn't be specific they wanted me to pay hundreds of dollars for a more detailed diagnosis but more or less he said no communication bad sensors which i have changed and my tire size was wrong i have a 225 tire instead of 215. I took the van back home and my husband checked all the wires they looked good but the actual tcm looked very rusted and one of the pins was shorter than the rest. Could the tcm be burnt out, should i just replace the tcm or is there something else i am missing.
Thank you

Answer
Hi Nicole,
It is crucial to getting a 'handle' on this to know exactly what the fault code numbers are. If you have an Autozone parts store or other nationwide frachise parts store nearby then go there where it is likely they will give you a free code readout and tell you the numbers and what they mean.
Another very easy way to get the numbers of the codes is to use your ignition key: turn it
"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window on the instrument cluster to see the mileage reading will change and instead show 4-digit numbers, precedes by a P.  Then write me back with the results. I can't tell what is going wrong so far from your description...is it the engine or the transmission that seems to be the problem?
Roland
PS Sorry for the delay but I just found your question in the "pool" to which it had been referred by another 'expert'. Please 'rate' my answer, and where you see the question about a nomination for me to be 'volunteer of the month' consider giving me a 'yes'. Thank you