Speedometer no more ?

Well , My speedometer just quit on me ..well not exactly quit but I think it spun out , I am going like 45 - 50 mph and it only shows 20 - 25 mph at that time with 1000 rpm , weird. I was told it was 'burnt up'but I thought to myself , If it was burnt up , wouldn't that stop it from working period ? I dunno , what do you guys think about this ?

it might be time for a new VSS buffer. crawl under the car and check the connection at the sensor in the tail shaft of the transmission, clean it if neccessary and see if that helps