About a month ago i noticed my tach reading close to 4500 in 5th gear at around 70 mph. It jumps around sometimes reads normal then spikes and stays there. I have 4.10's and it usually runs around 2700-3000. Is my problem an electrical connection somewhere or should i just take it to a shop and let them figure it out. I am sorta mechanically inclined so i would rather not take it to a shop if i can do it myself. I also have a speed calibrator for my speedo(don't know if this matters).