I have attached info from a TSB that seems to be what you are discussing. You need to talk the dealer about this issue.
If you would like us to look into it more then please go to Auto Zone (AZ) or O'Reilly's (OR) and for FREE they can pull the codes to the car. Most important: Once they check your codes, if they find something and you don't get it fixed and need to get back with us, please make sure you tell us exactly what the code was, number and all. Example, if the code was E0568 O2 Sensor bad. Then make sure you give us all of that. While there for FREE also they can bring their tester out and check your battery and alternator.
A/T - OD OFF Lamp Flashing/DTC P1783/Shift Concerns
Bulletin No: 05-005/02
Last Issued: 5/21/2002
OD OFF LIGHT FLASHING AND DTC P1783
All 1998-2001 626 4 cyl. with automatic transmission and VINs lower than 1YVGF22C*15237083 and 1YVGF22E*15237083.
Some vehicles may exhibit an OD OFF light flashing with DTC P1783 stored in memory after driving at highway speeds for extended periods. There may also be ATF leaking from the transmission vent tube onto the air cleaner box as well as intermittent hard shifting. These symptoms may be caused by operating conditions that cause the ATF temperature to exceed 135 degrees C (275 F). This concern is most likely to occur after extended periods of highway driving when air temperature exceeds 100 degrees F.
Customers having this concern should have their vehicle repaired using the repair procedure shown.
NOTE: This information applies to verified customer complaints on vehicles covered under normal warranty. Refer to the SRT microfiche for warranty term information.
Tuesday, December 23rd, 2008 AT 9:31 PM