check the cable first! alot of times they back out of the speed pick up in the tranny. if your sure it's in all of the way, then take it out and spin it with your fingers. the speedo should jump if it's working. (i put a makita cordless drill on the cable and it makes the speedo read about 30mph, but drill has to be in reverse though!) if the speedo doesnt work, then it's either a bad cable or a bad speedo. if it does work, then your pick up on the tranny is prob. bad.