Speedo/cruise control problem

I have a 2006 Volvo VNL with an ISX motor and a Meritor 10 speed. In the past few days a few weird things started happening all at thesame time (which makes it harder to pinpoint the problem). After hitting 50mph my speedo is hunting usually hovering around + - 5mph from actual speed. When in cruise control it hill hunt on rpms and cruise keeps shutting off. I replaced the speedo sensor on the transmission and no change. Cruise works fine when parked. Also my truck is governed at 65 but there are times it will cut off at 60 or 62 like it was governed at that speed. My fear is that the ecu has gone bad and im hoping it could be something smaller. Please help, i do a lot of the work myself on the truck so any sensor, wiring harness i could change my self before i go and spend crazy money on an ecu at a dealer.