[Boss Hoss]

Some how or another the kids managed to brake my lense covering my speedometer. I procrastinated on fixing the lense and one day i look down at my speedometer and the needle is sitting well below 0...looked like i was going -30mph(this just happened to be right after i had my truck detailed and im pretty sure they stuck their finger in there and fooled with it but i cannot prove it). Back to the issue at hand...i can manaul put the needle on 0 and seems to work fine untill i turn the truck off then it reverts back to -30 everytime. Am i going to have to buy a new cluster or does anyone know of an easy fix for this?