Ok, your tranny is stuck in what is called Limp Mode, here are possible causes.
In-Put/Turbine Speed Sensor Failure
Out-Put Speed Sensor
TCM - Transmission Control Module
next would be the tranny itself - the front pump failed or internal damage.
Changing out the 2 sensors is the cheapest and easiest first step cost of about $35 for both.
Sunday, January 2nd, 2011 AT 4:52 PM