It sounds like you have a shift solenoid or the input shaft speed sensor that is out but to be sure you need to check to make sure you do not have any codes that could lead you to the problem. Also, what color is the transmission fluid?
Here are two guides to help us get started.
https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing
and
https://www.2carpros.com/articles/how-to-service-an-automatic-transmission
Electronic Components
13 - TFP Manual Valve Position Switch Assembly
46 - Input Speed Sensor
62 - Output Speed Sensor
305 - 1-2 and 2-3 Shift Solenoid Valves
305 - 1-2 and 2-3 Shift Solenoid Valves
312 - Pressure Control Solenoid
335 - TCC Control PWM Solenoid
Check out the diagrams (Below). Please let us know what happens.
Cheers
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Saturday, November 5th, 2011 AT 2:13 AM