the stock tach in my car decided to go all wacky on me and now at idle it sit around 4000rpm. is there any way to fix this without replacing the cluster or do i need to buy a new one. if i were to buy a new one, what is all involved in the swap? do i have to move all the needles and roll the mileage to where i need it? by the way it is a 140 speedo so i dont have to upgrade it from the 85. thanks