97 Dodge intrepid tranmission

I have a 97 Dodge Intrepid with the 3.5 liter. The car has 195,000 miles on it and the engine is in great shape. I brought the car brand new and i kept all the maintance done right down to the teeth and log in my book. However, recently i check the engine light with and OBII scanner and pull code 731 (gear ratio 1 incorrect), 733 gear ratio 3 incorrect, 700 (trans. control system malf.). I work in a auto part store so I can have many of my parts tested. The car will not shift to 3rd or 4th gear instead when i get to 40-45mph it slip like if it was in netural. All this happen after a 5 hour trip of highway speeds of 70 to 80mph. The last 6 miles home where slow. (Check the fuild for burn, its ok) I let the car cool down overnight a reset the OBII codes. Drove the car to work (3 miles) and the same thing still happen. Recheck the OBII codes and now it telling me 733 and 700 only?? Where do I began? Since i work in a parts store I talk to many mech. that purchase parts from me and all they wants is to rebuild my tranmission because to the miles on the car. Could it be just the two speed sensor?

Here's one of two things that you can do: 1) Go back to a Chrysler dealer and have the TCM flashed programmed to update its operating parameters. 2) Change out your transmission fluid and run nothing but Mopar ATF +4. Chrysler transmissions are very sensitive to the type of fluid you put in them and if you use anything else, it will act up and give you problems. If you have 195,000 miles on the original tranny, I take my hat off to you. I rebuild tranny's and the most mileage I ever saw out of an Ultradrive transmission (A-604 & A-606) was 172,000 miles. A rebuild is another possibility with the high miles, so those other mechanics who tell you that are also right. But try first the flash programming and fluid change.