Im stumped here. Ive tried everything I can think of. I have a 2002 Jetta TDI automatic. Normally the vehicle drives and shifts fine but over night it seems to be shifting different. Not it wont shift gears until the RPM's hit about 3500. That is way higher then before. It has a very hard time shifting from 3rd gear into overdrive. The only time it will even go into overdrive is if im at 3500+ RPM's which is about 65-70 which is well over all the posted speed limits around here. I know this is KILLING my fuel mileage. I have tried disconnecting the battery for 30 seconds and putting it back on. I tried cycling the key 2 times and holding the gas pedal down for 5 seconds. Still nothing is working. My engine did over heat a little the other day because I lost my coolant temp sensor, put a new one in and filled up the fluid and thats back to normal. Not sure if that might have something to do with it. Any help would be great. Thanks