03 Durango with a 4.7. Doesnt seem to matter speed and doesnt happen all the time, but while driving my tach drops to 0 like I've just shut my vehicle off but it's still on. If I let off the accelerator it comes back. Just had ecu refurb and reflashed due to a no bus issue. Had this issue once in a blue moon prior to the r&r. I have a cable throttle not electrical so I dont see this as an issue. I'm at a complete loss.