I am thinking its thermostat time - thoughts out there? Driving to work in the morning, the gauge wont really move off about 140 until I get off the freeway and it goes up a little. After warming, it used to ride consistently dead center. Now it only goes there when its real warm or I'm towing. Gauge or thermostat or... thanks...

 

My 2002 was doing about the same and a new thermostat fixed it up. If you can get an oem one from cummins or the dealer. I needed one right away and had to settle for one from our local carquest store. It is decent and better than my failed oem one but about 10 to 15 degrees cooler than what my oem one was.