More than likely it is a shift solenoid or the pump is not supplying the pressure needed to hold a gear. This could be due to a faulty pump, O-ring seal or other internal passage problems such as blockages.
Start by getting the trouble codes pulled. Any Advance Auto or Auto Zone will pull the codes for free and make diagnosing the issue much easier.
Get those and get back to us and we will work through the problem.
Thursday, October 20th, 2011 AT 1:14 AM