So my Tachometer has been jumping sparaticly and sticky since 80,000 miles, i now have 160,000 and still having that issue but has been the same, not getting worse. I was hoping it would just fail but thats not happening soon, any idea whats causing it to do that? Almost at the point where i am sick of it..

 

This sounds like the problem I had with my old T-Bird. The tach in that vehicle got it's input from the distributor or the coil primary as I recall. The contacts in the harness there became dirty/corroded and once I cleaned them up, the problem went away.

On the more modern trucks, the signal comes from the PCM.

- Jack