98 explorer 4.0 speedometer

whats up with no speedometer on these things? all other gauges work fine, but speedometer comes and goes! I have vss signal at sensor, and i've never seen speedometer head go out on these; yea i know there's always a first time, but could it be gem or ecm? How can i check for these? I'm a small garage with limited resources; so i rely on help from others that may have seen this problem before! Thanks for any help greatly!!!!

The speedo in my wifes explorer did the same thing. Her's is a 98 AWD. The plastic circuit board on the back of the dash seperates and does not make connection. I pulled it apart and added jumper wires from the connector to the speedo and have not had a problem since