96 Ram 2500 Diesel Problem?

Hello, i was wondering if anyone could give me some insight on a problem? The Truck's speedo and Tach, go crazy whether driving or at idle, the warning lights also come on and the truck downshifts. It is a intermintant problem, had a palm pilot on it even while the truck was acting up and there are no codes? Any help would be greatly appreciated!
Thanks

I had a 95 with the Cummins. I had a problem that led to it not going into overdrive. Ended up being the Throttle Position Sensor. About $100 back then. Easy for a do it yourselfer.