Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
Hello, from what I am seeing in your description I would say the most likely problem is the dash itself. Chevy trucks in the 90's and early 2000's had lots of issues with the dash going bad. I have had to replace many of them for needles bouncing not just the speedometer but other gauges as well. This normally is not a sensor issue as when the sensor fails the gauge will not read at all or will read steady but inaccurate. I hope this is enough information to answer your question.