What controls the overdrive clutch in my 2000 Dodge Durango?

"I'd take it to an Auto Zone and get a free readout of the computer. This sounds like a throttle position sensor problem to me. Here's how it's replaced, but do the Auto Zone check first and ask them.

http://www.ehow.com/how_4590653_replace-..."

"Whether or not your vehicle shifts into overdrive is a combination of road speed and RPM. The shifting is controlled by the valve body. If you are going uphill or accelerating, then your transmission will downshift which makes the engine's RPM go up to maintain your speed.

Are you going up or down hills when it kicks in/out of overdrive or are you speeding up to pass someone? If not then, it could be a problem with the valve body, clutches, or maybe the torque converter.

It has been awhile since I worked on automatic transmissions, but this is what I can remember."