In the past day or two, my speedo has become tempermental. If the truck sits for any period of time, the speedo won't register for a few blocks or until I tap the dash, then it works fine until I shut the truck down again. The odometer seems to work okay. I checked the grounds, connector and speed sensor but the problem is still there.

I'm leaving for Oregon in a few days and don't need to have problems on the road - any ideas what may be causing this?