1995 speedometer and odometer problem

I have recently acquired a '95 2500 with 5.9 12 valve and 47RH auto trans. When cold the speedo and odometer usually do not work at all. After driving for a few miles both will start to work but the speedo will be reading almost twice the actual speed and bouncing. On a longer trip the speedo may start to work correctly. At all times the cruise control will be working correctly. No check engine lights or abs lights are on except prior to starting as they normally are. I suspect the instrument cluster. Any suggestions?