umm
what size rims do u have?
anything bigger then stock will throw off ure speedometer. fyi. also it might not be able to be fixed, prob just needs the little chip off the back of the speedo. go to a junkyard, pick one up for 10$, if your slick, free
im not telling u how to get one for free, but maybe u can get the idea. have a replacement, be nice
btw, its cold, so wear a jacket bring ure own tools
umm other then that, thats what i suggest, i had a simlar problem, the litle chip is what you need.