Volvo Speedometer/cruise gone crazy

I have a 2001 VN 770. Signature 500 pre-EGR. EF 13spd. The problem began with cruise control not working properly. In use it would kick out for no appaerent reason.
I replaced engine speed sensor, TPS and RPM speed sensor. It seemed fine for about 3 weeks then it started over with a twist. The speedo now is very errartic.
At idle its reading varing speeds from 5-50mph. When driving it fluctuates up and down. The only thing I can think of that could cause this is the actual
dash panel itself and the ECM. Both parts are very expensive so before moving forward I am calling on some advise from my fellow drivers and techs.
Fire away with your suggestions please. Thank You

 

Already replaced... Next lol

 

Thank You to All for your help. I have found and resolved the problem. I went ahead and purchased a speed sensor to replace since it was a nomial price of less than $30.
While replacing it and inspecting the yolk I began tracing the wires. only had to go back about 4 inches from the sensor to see where the problem was. Yep wire had rubbed enough insulation of to cause it to short when the truck would bounce. Sometimes touching sometomes not. This was the cause of the intermitan speedometer and cruise conttrol issue. Hope this help someone else in the future and again I thank all. Be Safe Out there. Your loved ones need you Home.