Tach, Speed, Gas Guage

I have a 95 Jeep Cherokee... the other day the Tach and Speedometer would quit working for brief periods, but start working all of a sudden when I would hit the gas or brakes... to give it a jolt. On the same day, the gas guage would sporatically peg way past "full"... almost to horizontal. After that one day, the speed and tach are completely out, and the gas guage is permanantly pegged past full.
Anyone heard of such a thing?

Bad ground wire for the entire instrument cluster. The tricky part is finding where the ground wire is, likely its just a loose screw.