P0700 2005 DODGE DURANGO?

got into my durango last week to go to work started fine reversed fine. Then I put it into drive and in 1st gear the engine was wailing/racing with a loud noise but the rpms were at 1,500. It shifted into 2nd fine and drove great for the rest of the day. Even when I would start out in 1st gear again it was fine. Then yesturday the same thing happened in the morning and again it was fine after it shifted into second. When I got into my car after work the Malfunction Indicator Light"Check Engine Light" came on. I did the key trick to check the code and it was P0700. I know what the code is. I know its telling me that something is wrong in the Trans or TCM. I'm going to the dealer in 2 days because I'm working but the Durango is sitting at home while I drive the van to work. But my question is what part or sensor is broke or in need of repair. I'm not a big car guy so help needed!